Answers to discussion topic questions to Unit 1

Answers to discussion topic questions in Unit 6

Please make sure you understand the answers before you attempt the practice quiz or unit test. Many of these answers came from your fellow students.

Tough Laser questions (which will not be on the test so please just skim over)

When a hologram is backlit by a laser, a 3 dimensional image appears. The laser light is diffracted as it passes the narrow patterns of dark and light imprinted on the hologram. How does that work? That is, explain (in terms presented here) the process of diffraction as monochromatic light passes through two narrow slits. Hint: This is a common experiment in physics. A series of bright spots appear away from the center. Why?

This is an example of constructive interference. That is, when two waves meet "in phase", they reinforce each other. It should be apparent that if a wave front hits the double slits at the same time, there must be a bright spot directly in front (on the screen) because light from both slits travel the same distance. That is, if they were "in phase" when they reached each slit, they have to be "in phase" when they reach the center of the screen. However, why is there a bright spot off to the side? Again, constructive interference! The waves arrive "in phase" at that spot even though the path taken from each slit is different. The key is understanding how big that difference is. If the path difference is exactly equal to the wavelength of the light, then the beams arrive "in phase" and a bright spot appears.

animation

2.     If someone gets the first question correct, someone else should try explaining why a diffraction grating is capable of breaking white light into the full spectrum. (also NOT on the test)

A diffraction grating is nothing more than many slits imprinted on a slide. It is used to break white light into its component parts (rainbow) just as you might expect in a prism. If you understand the famous "double slit" experiment, you may be able to see why a diffraction grating works.   The wavelength of each color in the visible spectrum is different. Blue has a shorter wavelength than red light. Therefore, you would not expect constructive interference at the same spot on the screen for all colors. You would expect blue light waves to be "in phase" a bit closer to the center.

animation

If you were able to digest all this, you may have a clue how holograms work. The hologram itself is nothing more than a very complex pattern of a light and dark images on a plate which act like a diffraction grating. To get bright spots to appear off to the side, you need to rely on constructive interference. Now I'll toss in one last twist and you may start seeing the light (pardon the pun). You can also control where (on the screen) the bright spots appear by altering the distance between slits. The closer the slits are, the more "spread out" the interference pattern becomes. This applet lets you see this in a virtual environment.

Application of Lasers - The great part of this class is your instructor can learn from the student. Below are some posts I've never heard about until you told us.

New televisions will incorporate lasers. These TVs also known as LPD TV have a glass matrix display that have red, green and blue phosphor that glow when a laser is used. So you can add this technology against LCD and Plasma TV when shopping for a new TV (probably not in the near future). Source Note: It looks like a laser replaces the electron beam in older CRT (cathode ray) TVs.

Sound

Why do acoustic guitars have a huge air cavity set behind the vibrating strings?

The strings of a guitar displace a tiny volume of air so there is a need to amplify the sound. The vibrating strings make waves that hit a thin piece of wood called a sounding board. This is designed to resonate at many different frequencies. This, in turn, forces waves into the cavity. The cavity acts as a resonance chamber. That is, waves reflected off the back of the guitar interfere constructively with incoming waves to produce a louder sound. The sounding board typically has a hole that allows these waves to escape and reach your ear.
You can usually tell when your car's fuel tank is about to be filled by the distinct sound coming from the fuel port. Describe that sound and offer an explanation why it occurs.

The sound is a progressively higher pitch as the gas fills the tank. The pipe leading to the tank acts like a resonant chamber. To amplify the sound, we need to send out waves at a given frequency (wavelength) so that when one compression wave is created, it moves down to the gasoline, reflects off the surface and moves back to the opening just in time to meet the next compression wave. This will make a louder sound - constructive interference! Consider two cases - case #1 where there is a long cavity of air and case #2 where the air cavity is shorter. In both cases the air (at all frequencies) travels at the same speed. In case #1 the wave must travel a longer distance so a wave with a long wavelength (low frequency) is needed. As the air cavity shortens (as in case #2), the wave travels a shorter distance. Resonance can only occur if the wave has a shorter wavelength (higher frequency). You can experience the same thing if you have ever played with a slide whistle.
Describe why a jet flying at the speed of sound produces a sonic boom soon after it passes by.

This is constructive interference at its best. Imagine you could pack all the sound your TV made during the last minute into one second. That is what a jet flying at the speed of sound (mach 1) is doing when you hear a sonic boom. When flying at mach 1, the sounds made from the jet move with the jet so that all the wave energy adds together to form a shock (pressure) wave. To see this, go to this page and use the slider to set the speed to 1.0 You can even see the shock wave in this cool picture.
Architects have designed special "whispering rooms" or "whispering galleries" with the property that a person near one end of the room can pick up faint whispers from a person near the other end of the room. How is that possible?

As you might guess, this is another example of constructive interference. The room itself is shaped in an ellipsoid. There are two points (called foci) where one person whispers and the other person listens. Sound waves emanating from one foci spread out through space, reflect off the walls and move to the other foci.
animation

Now, do you want to know where this idea can be more than just entertaining? Try deep brain stimulation! One treatment for Parkinson's disease and obsessive-compulsive disorder involves inserting electrodes deep in the brain to stimulate specific brain cells. In 2017, researchers found a noninvasive way of doing the same thing using a technique called temporal interference. Imagine the target neurons are located at the destination blue dot in the animation above. By mapping the individual's skull, several electrodes can be precisely placed on the patience's skull that behave much like the whispering room. All the energy of the individual surface probes constructively interfere at the target cells deep within the brain. So far this has only been tested on mice.
Have you ever noticed that on very cold mornings when the air is very still, you can hear very distant sounds (maybe a distant train or noisy car)? What is the scientific reasoning behind this phenomenon?

This one is a bit tricky. The speed of sound changes with temperature. The colder it gets, the slower sound travels. Under normal conditions, the air temperature drops with height. If you recall, refraction (bending of waves) occurs because of a change in wave speed. Under a normal atmosphere, sound waves are refracted upwards. This is why sound doesn't carry very far under normal conditions. However, if the atmosphere overnight is very still (and there is a clear sky ... so lots of surface heat escapes), the surface will be considerably cooler than the air aloft. Under these conditions (known as a temperature inversion), sound waves are refracted downward (actually it is more like reflection ... as in "total internal reflection" as seen in fiber optics). When this happens, the atmosphere acts very much like the whispering room in the last question. This allows very distant sounds to be heard as waves constructively interfere.

This is what normally happens to sound in the atmosphere ...... but not during a temperature inversion.

Here is an additional interesting atmospheric fact: You may have noticed that it is much quieter when it snows. This is because snow absorbs ambient sound waves and acts as a damper to make the area much quieter.
Earthquakes also emit another wave - known as surface waves (which include Rayleigh waves and also another type called Q, L, or love waves). Are these compression, transverse, or completely different type of wave? Explain.

This wave is actually responsible for most of the destruction to buildings and bridges during an earthquake. The surface wave only moves along the crust of the earth (hence its name). The L wave is a transverse wave (similar to the S wave discussed in the eBook). The Rayleigh wave is a similar to the waves we find in water where the motion of the water itself forms tiny ellipses. Together these two waves form the "surface wave". It is actually a combination of a compression and transverse wave. That is, displacement is similar to the behavior of a clump of mud stuck to the threads of a car tire. The clump moves both forward and up/down as the car moves.
animation
Mariners have reported extraordinarily high waves known as rouge waves. Do these waves actually exist and how are they formed? Answer this using information you learned in this section. Are they predictable?

Yes, rouge waves exist and are completely unpredictable. They form from the constructive interference of two or more individual waves that, by chance, crest at the same place at the same time.

GPS applications

Most all posts deal with the ability of a GPS to pinpoint the location of an person or thing. This can include kids, pets, prisoners, cars, and many, many more items. One student pointed out that the GPS is used extensively in marketing. Companies can target where to apply resources (such as advertising) based on where you are. The student used this example: If you spend most of your time at home, advertisers will keep this in mind and attempt to sell you products for home use or services to deliver items to your house. A GPS can also determine the speed and acceleration of an object (so you not only can track your kids location, but find out if they are speeding). But here is one thing most students miss ... time. Once calibrated, a GPS has atomic clock accuracy (without the atomic clock price tag). This ability of a GPS has many applications such as precise time stamps for financial transactions and synchronization of communications systems (such as power plants). More on this here.

Wave Modulation

TV and FM have a limited reception range, but AM and (low frequency) ham radios can communicate over great distances. Explain the difference and how this long range communication is possible.

TV and FM are "line-of-sight" transmissions. This is one reason why the transmitter is typically located in high places. AM transmissions and ham radios (which operate with a lower frequency) can reach a much greater distance because the beams are able to reflect off the ionosphere. In fact, they may bounce off the ionosphere and ground and travel all the way around the world (called atmospheric skip or skywave). As a kid, I was amazed to pick up very distant AM radio transmissions at night (I even built my own crystal radio). I later found that during the day, the sun ionizes the atmosphere in the D - layer (about 25 miles up) which absorbs AM frequencies. At night, this layer no longer exists so the waves are free to move higher and reflect off the F - layer of the ionosphere. Test this out at night with the AM radio in your car.

Another acceptable answer involves repeaters. Almost all long distance signals degrade with distance so repeaters are place between the source and target to boost (amplify) the signal.
Guglielmo Marconi first transmitted a transatlantic wireless message in the early 1900's. What message did he send? Was this AM, FM or some other kind of wave modulation? Explain.

As early as 1895, Marconi was sending Morse code signals over short distances (about 1 mile). He sent the message "are you ready" in Morse code over a distance of about 9 miles in 1897. However, his greatest feat was the transmission of the Morse code for "S" (three dots) which was sent over the Atlantic ocean between England and Newfoundland in 1901.

Marconi's transmissions were neither AM or FM. He used another form - pulse modulation. It was called "spark-gap" transmission (just static .. but on/off static to convey a message). It is basically a step up transformer which is allowed to discharge across a small gap as an electric discharge (much like a spark plug in your car). Any time you can get electrons to jump the gap, electromagnetic waves are produced. This way, you can form dots and dashes to communicate via Morse code. Note: Have you ever noticed an older TV or AM radio picking up static when the vacuum cleaner is on? The small sparks in the brushes of the motor are emitting radio waves. The next time there is a storm, turn on your AM radio and listen to the lightning.

I found it interesting that "pulse modulation" to send a message (via Morse code) is back in the news. Instead of turning an electromagnetic wave on/off, it involves a beam of particles called neutrinos. Here is what a student sent in from the next section ....

Scientists were able to send the first message through rock using a beam of neutrinos, which are subatomic particles with no electric charge, almost massless, and travel close to the speed of light. The message sent was “neutrino.” Neutrinos (for communication) are unlike electromagnetic waves. They pass freely through solids and liquids because they are not “disturbed” by gravity or magnetic attraction. With more research and improvements in technology, this complicated system could be used for submarines that need to communicate over long distances through water. Source
Long before wireless communication became a reality, telegraph systems were able to transmit multiple signals over one wire. That is, sender "A" could transmit a message to receiver "B" at the same time sender "X" was sending a message to receiver "Y". This was an early version of a "tank circuit". How was this done?

This question is very tricky and was done by modulating the signal at the transmission point. The animation below shows two transmitters on the left. A bell is placed in series with the key. When the key was pressed (to make a dot or dash), it would activate a bell. The clapper of the bell was held back by springs with a specific tension. This would break the signal into pulses of varying frequencies (depending on which transmitter was used). Note: I left out the wiring details.

At the receiving end, the same bell becomes the output. Only a bell tuned to the correct frequency will ring. That is, the spring tension controls the resonant frequency. Only a signal with the same frequency will ring the bell. This way Joe can send a message to Sam and Sue can send a different message to Mary (over the same wires) Source: Thinking Physics by Epstein & Hewitt
There were many different methods of multiplexing (which is what this is called). I just described Frequency-division multiplexing. Let me give you another acceptable answer (which is much easier to understand). Let's say you want to use one wire to send 5 separate signals. All you need to do is give each sender (and receiver) equal time to the wire. A timer switch is set up (at each end) so that each user has solo access 20% of the time. Information is buffered until the gate opens for your signal to pass. This is known as Time-division multiplexing. Want to go deeper into the rabbit hole? Remember last unit when we discussed polarized light? Ok, now use an optical cable and send multiple signals down it ... each with its own orientating of polarization. Polarized filters at the receiving end can isolate your signal from all the rest.
In mathematics, there is a technique known as Fourier analysis. It is extremely complex in its application but simple to describe (easier said than done). Please describe in simple terms what this technique is. Then relate your answer to your experience when listening to music.

When you listen to music, what reaches your ear is the wave sum of all the individual instruments and voices all rolled up into one very complex pattern. However, you have the amazing ability to listen to the music and focus on any individual instrument or voice and isolate it. Fourier analysis is a technique that does much the same. It is an attempt to take any complex wave pattern and break it into the sum of several individual sine waves. Once done, it can be useful in many ways. For example, when you touch tone a number on your phone, the signal is superimposed with the line frequency. On the receiving end, Fourier analysis is required to isolate the two waves and determine which key was pressed. The same technique is used to filter out the vocals on a karaoke track.

Waves as Probes

Offer a brief overview how the Scanning Electron Microscope (SEM) works

First the sample needs to be prepared for scanning. The item is coated with a thin coat of gold or carbon and placed in a hard vacuum. A beam of high speed electrons is focused to a tight beam (1 -5 nm) using magnetic fields. This beam can also be manipulated (side-to-side) by magnetic coils (much like they are in a CRT). When the primary electrons strike the surface of the sample, they are scattered. This ejects secondary electrons from the surface which are recorded by detectors. This is rendered into an image and enhanced by a computer to show the contour of the surface. Source: http://sciencepub.org/nature/0403/03-0171-mahongbao-ns.doc
Offer a brief overview how the Scanning Tunneling Microscope (STM) works.

Blind people can use a cane as a probe to gain details about their surroundings. A STM works the same way. A very small probe (called a stylus) comes very close to the surface to be scanned. The tip of the stylus is only one atom wide. When this probe comes very close to the surface (and a voltage is applied), electrons will move between the surface and the probe (this is tunneling). Since this current changes with distance (between probe and surface), it is possible to move the probe so the current remains constant. This way, you track the surface by measuring the motion of the probe.
Telescopes suffer from the same resolution limitations as microscopes. As a result, you would expect that radio telescopes offer poorly resolved images due to the longer wavelength of radio wave. However, that is NOT the case due to another technology called arraying. Briefly explain how this technique has vastly improved resolution in astronomical applications.

An innovative technique used by large telescopes uses interferometry (or arraying). If you review the class material related to resolution (resolving power), you will see that resolution increases with the diameter of the mirror. Clever engineers realized that you can place individual telescope mirrors apart from each other and linked via high speed computers to achieve the resolution of one giant mirror that is as big as the separation. Stated in another way, the farther the individual scopes are from each other, the better the resolution of the image. This system greatly improves the resolution and was first used in radio telescopes. It is now done in the visible part of the spectrum as well.
animation

Reflected waves

This is not earth shattering but some newer cars are equipped with rain sensors to automatically activate the windshield wipers. It works because a device mounted in your rearview mirror sends IR radiation towards the front windshield at a slight angle. If raindrops are not present, you can expect a certain amount of reflection back to the mounted device. However, the amount of radiation returned to the sensor changes if drops of water are present on the glass.

Where I work we test if cables are good by using a TDR (Time-Domain reflectometer). Basically it sends a pulse down a coax cable. If the cable is good, it passes to the end unobstructed. If the cable is bad, the pulse is reflected back and this tells us there might be a twist or bend in the cable.

In the industrial world a type of ultrasound known as ultrasonic testing, is often used as a way to check for internal flaws in materials such as steel or defects and leaks in pipes. Because you cannot see inside of piece of steel this is very handy to know if there would perhaps be a bubble or other weak point within the material. It can also be applied to materials such as concrete.

Great discoveries made by observing an unexpected type of wave (or a wave from an unexpected source).

The idea that the entire universe came from a singe event known as the Big Bang came from the accidental discovery that there are faint microwaves coming at us from all directions. This is known as the cosmic background radiation discovered by Arno Penzias and Robert Wilson in 1964.

Pulses of X-rays from Cygnus X-1 (a star in the constellation Cygnus) led astronomers to believe that it has a black hole as a binary companion. You cannot see a black hole but its existence is inferred by the behavior of the visible star. It is believed X rays are produced as the black hole pulls material off the companion which superheats as it funnels to the event horizon.

Einstein put another feather in his hat when gravitational waves were discovered in 2015. These are waves that represent ripples in the fabric of space (and time) which were likely produced when two black holes merged. These waves were not unexpected ... but never detected despite years of observing by the LIGO observatory. The discovery provided one more piece of evidence that Einstein was correct.

Great discoveries made by using a beam of particles

About a century ago Ernest Rutherford sent high speed alpha particles (helium nuclei) at a gold foil target. He noticed that most went straight through but on rare occasions, some were deflected (even sent back to the source). He concluded that a majority of the atom was empty space and that most of the mass was concentrated in a very small volume which we call the nucleus.

One common medical scan is known as a PET Scan. This stands for Positron Emission Tomography. The key to this technique relies on the fact that cancer cells take in glucose at a higher rate than normal tissue. Therefore, a radioactive isotope (with a very short half-life) is attached to the glucose. When injected into the body, this isotope concentrates in cancer tumors. During the decay of the radioactive isotope, a positron is emitted which interacts with a nearby electron ... producing gamma rays (as a pair moving in opposite directions). All you need to do is make an image from these gamma ray emissions to discover the location of the tumor. A similar technique (called SPECT) is used in nuclear medicine to map your cardiovascular system or to perform a bone scan.

If a fire breaks out in your house, a beam of particles may decide if you survive. If your fire alarm is the "ionization type", it consists of a small amount of Americium 241 ... a radioactive substance that emits alpha particles (the same thing that makes up the nucleus of a helium atom). These particles have the ability to ionize oxygen and nitrogen (the stuff that makes up air). Now place two plates close to the Americium 241 and give each plate opposite electric charges (with a battery). Under normal conditions (no fire), the ionized particles will be attracted to the appropriate plate which constitutes an electric current. However, if there is a fire, the smoke particles are able to neutralize the ions and no current results. This is sensed and triggers the alarm to go off.

Physicists are trying to understand what the universe was like just after the "Big Bang". In that effort, they have constructed a particle smasher known as the LHC (Large Hadron Collider) in Europe. By accelerating and colliding protons and lead ions at nearly the speed of light, they are hoping to find a particle known as the Higgs boson. Why? Discovering the existence of this particle will confirm theories cosmologists use to understand the nature of matter and how our universe evolved. Good news .... in 2012 the Higgs boson has been found..

Great discovery made by studying an absorption spectrum

All stars emit an absorption spectra. The lines not only tell the chemical composition of the star, it can also tell the temperature of the star as well. Early astronomers thought that strong absorption lines from a specific element meant that the star had a lot of that element in its chemical makeup. Wrong! It turns out, the strength of the lines (how well defined they are) depends on the temperature at the surface (photosphere). All stars are mostly hydrogen and helium, and only a handful of the rest of the elements. Stars are classified by temperature on a scale OBAFGKM - O being the hottest and M being the coolest. This is obtained by noting which element's absorption lines are the strongest and most well defined.

Give one application where the Doppler Effect is used to obtain the speed of an object or investigate how something is moving.

Since all stars have absorption lines, they make a great reference mark to measure their speed (via the Doppler effect). That is, the lines are blue shifted if it is approaching and red shifted if receding from us. For example, if two stars are binary companions and their orbital plane is in our line of sight, one star will be approaching us at the same time the companion is moving away from us. By measuring the Doppler speed, one can establish how the mass is distributed in the system by comparing speeds. If both stars have equal mass, the speeds will be equal. However, if one star is very massive and the companion has a low mass, the Doppler shifts will show that the high mass star moves slow and the low mass star will move with a much higher speed. If interested, see http://ecampus.matc.edu/mihalj/astronomy/test3/doppler.htm (the applet says it all).

The Doppler effect is used to monitor heart movement. This process is known as echocardiography. This is a process of using sound waves to create an image of the heart.

A Laser Doppler vibrometer (LDV) is used to take measurements of a surface through vibrations, without coming in direct contact with the surface. This makes it beneficial for use in areas where contact is not possible because the surface may be too difficult to reach or when it is not possible to come in contact with the surface in general, such as when it is used in the detection of land mines. LDV's are also used in the architectural industry for bridge and structure vibration tests, in the automotive industry for structural dynamics and brake diagnostics, and in the medical field for eardrum diagnostics.

Give any example (not already mentioned) where a wave passes by an object and is effected (in any observable way) as a result. Has any great discovery ever been made using this idea?

One type of smoke detector is a photoelectric type. The animation below shows that if no smoke is present, the light never hits the photo sensor. However, if smoke is present, some of the light is scattered in the direction of the photo sensor and an alarm sets off.

animation of a photoelectric smoke detector

One phenomena is known as a gravitational lens. Einstein showed that light is refracted by a gravitational field in the same way light is refracted by a lens. If something were in deep space and had a lot of mass, it would be possible for light rays to focus its radiation to the earth (of course, the geometry has to be right). Guess what? Astronomers have seen this effect several times and are convinced that the universe has MUCH more mass in it than shows up in our detectors. This mass is called "dark matter" and could make up most of the universe.

Want more astronomy news? Einstein predicted something called "gravitational waves" would result from the merger of very massive objects (like black holes or neutron stars). In October 2017, gravity waves were detected from the merger of two neutron stars. Some really clever astronomers determined that it is possible to determine the distance to the event by measuring the strength of the incoming wave at the detector. In theory, the merger of neutron stars should produce a wave in gravity with a known amplitude. As that wave spreads out, the amplitude decreases at a known rate, allowing you to predict how far away the event occurred. As an analogy, if you toss a rock in water, the waves spread out and the amplitude of the wave decreases with distance. If you know how big the wave was to start with, you can predict the amplitude of the wave at any distance.

Airport Security

The next time you visit the airport, you could walk by a "hands free" security check point. There are two types of scanners used for airport security - the Backscatter scanner (which is nothing more than a low level X-ray scanner) and the Millimeter Wave scanner. In this technology, two rotating antennas emit radio waves that are directed toward your body and reflect off your skin. The reflected waves are collected to produce a 3-D image. Any metals, plastics, or liquids between your skin and the receivers show up on the image. Busted! This same machine can be used in the fashion industry. Imagine getting "fitted" in a virtual dressing room. This has already been used in some Fashion Bug stores under the name - Intellifit.

Rogue waves! These types of waves are known as killer (ocean) waves because they can sink a ship in seconds. Back in 1995, this wave appeared on a scientific instrument which recorded this wave up to 80 feet high making it three times as high as a normal wave. Rogue waves are many waves united together to cause complete destruction in the sea. Note: Ironically, the destruction of a ship is caused by constructive interference of random ocean waves.

CyberKnife is a relatively new way to destroy cancerous tumors. Basically it is a device that is able to emit cancer killing X-rays that enter the body from many different directions which intersect and concentrate their energy at the site of the tumor ... destroying it. No scalpels, no pain, and very few side effects. I know, I went through this procedure to (hopefully) cure prostate cancer. An even newer approach is to do the same with a beam of protons (instead of X-rays).

Nanotechnology

Biotechnology is a subset of nanotechnology in that it uses living tissue (cells) to make something useful. One could argue that biotechnology has been around for a long time since biologists have long been altering genes to grow hybrid crops that grow in new or stressed environments, become resistant to disease, produce higher yields, or simply taste better. However, let’s go beyond agricultural applications and discover some insanely interesting ways biotechnology has (or will) make our lives better.

As a model, let me introduce one application that uses biotechnology to make a game changer in the field of fuels.

Several private companies are in a race to find a way to use simple grass (and other waste biomass products) in a process to make a combustible fuel. Rather than using the tradition method of fermentation to make ethanol, the twist is to genetically engineer e-coli or algae to digest the biomass and “poop” out fuel. The “cellulosic ethanol” not only emits less carbon dioxide but uses biomass that is not in direct competition with the food industry.

Now it is your turn. Find something specific and interesting in the field of biotechnology and post away.

Note: This is a new question so I will post future applicable posts

In Richard Feynman's paper, he mentions the possibility of writing at the atomic level, and it has since been accomplished. What was the first message written at the atomic level?

Direct quote from http://ngm.nationalgeographic.com/2006/06/nanotechnology/did-you-know-learn

Feynman offered a $1,000 reward for the first person to shrink a page to 1/25,000 of its size and show that it is still readable through an electron microscope. In 1985, a graduate student at Stanford named Tom Newman used an electron beam to write the first page of A Tale of Two Cities, by Charles Dickens, at 1/25,000 its original size on the head of a pin. He put together a package with the pin and the evidence supporting his work and mailed it to Feynman. Within two weeks, Feynman sent back a check.
What is the current record for writing at the atomic level? That is, how small is the message, what is the message, and who accomplished it?

The letters IBM were written with 35 xenon atoms in 1989 by ... (duh) IBM. However, a new record was set in 2009 by Stanford University by writing the initials "SU" only .3 nm across.
At the time of his paper (1959), Richard Feynman claimed the electron microscope had a resolution limit of 10 angstroms. Convert that to nanometers. What resolution did he hope to achieve? Has this been accomplished?

10 Ǻ = 1 nm (nanometer)

Feynman hoped to achieve a resolution 100 times better ... or .1Ǻ

The closest (I've found) is .6 Ǻ by a Z-contrast scanning transmission electron microscope dated 3/2005 (although this link erroneously claims the Feynman limit has been achieved).

In a press release dated 11-08-09 from www.nanotechwire.com, work is beginning on the world's most powerful microscope, called the PICO project. It will have a resolution of 50 picometers (.5 Ǻ ) - in other words less than one hundredth of the diameter of an atom. ( http://www.nanotechwire.com/news.asp?nid=8916 ). This is getting very close to Feynman's dream.
What is graphene? Give its physical properties but NOT any practical applications. The applications of graphene are covered in the next question.

Graphene is a one atom thick sheet of carbon atoms formed in a honeycomb arrangement. Some compare graphene to atomic “chicken wire”. The graphite in an ordinary pencil consists of flakes of graphene. The difference is that graphene is one continuous sheet. A carbon nanotube is essentially a rolled up version of graphene whereas this form is strictly a 2-dimentional object. This substance is stronger than steel.
List at least 3 (potential) practical applications of graphene. In each example explain the role graphene plays in the application.

Note: All of the following are years away from practical use.
The electrical conducting properties of graphene can be altered by the presence (or lack of) an external electric field. As a result, graphene could used to make extremely small and efficient transistors. This could be big news for the computer industry some day.

Gas molecules that land on the surface of graphene can alter its electrical conductivity by changing the overall resistance (which can be monitored). As a result, graphene can be used as a gas sensor.

Graphene is resistant to attack from strong acids and bases. As a result, a sheet of graphene could act as a protective layer from these corrosive agents.

Because graphene is essentially transparent and can conduct electricity, it may be used in many optical applications such as touch screens and liquid crystal displays.

Graphene has excellent heat conduction properties. As a result it can be used as a "heat sink" to draw heat away from hot spots in electronic devices.

There are likely many more potential applications for graphene. This is just a short list.
What is carbyne, what are some its physical properties, and how can it be put into practical use?

Unlike graphene which is a sheet of carbon atoms, carbyne is a string of carbon atoms that forms very strong bonds with adjacent atoms (like links in a chain). In addition, one string of carbyne will form “cross-link” bonds with adjacent strings of carbyne. This makes carbine stronger than graphene or diamond. Since this material is fairly new, the practical applications are still a mystery but some scientists have suggested that stings of carbyne could act as energy storage medium (resulting from the “cross-link” bonds formed between adjacent stings).

The Nucleus

The equation E=Mc² was shown (in the eBook) that mass can be converted into energy. Has there been any instance where the reverse occurred? That is, where energy has been converted to mass?

Technically ... no ... not in the lab at least. There is a counterpart to all particles we call antimatter.. A positron is a positively charged electron. There are antiprotons, antineutrons, etc. When a particle of matter interacts with its antiparticle counterpart, they annihilate each other and produce pure energy in the form of electromagnetic radiation (high energy photons). The opposite of this reaction has been predicted, in theory, where two (gamma range) photons collide and create an electron and positron. The problem is, most particle accelerators (like the Large Hadron Collider) only smash particles together .. not radiation. Some scientists believe this can be done with existing technology but that has still not been done experimentally.

Just because we have not done this experimentally (yet), the theory is so well established that there is little doubt that this process is possible. Astronomers believe the universe started with a Big Bang ... of energy. The conditions were so extreme that these photons would collide, producing all the matter we now see in the universe. The problem is ... where is all the antimatter? That problem is still unanswered but may be explained if unstable antimatter decays at a different rate than ordinary matter.
Briefly explain what went wrong at the Chernobyl nuclear power plant in 1986.

Chernobyl was a disaster in design, procedure, and human error. Technicians realized there was a design flaw in the power plant. They wondered if emergency power could be supplied to the cooling pumps by the inertia of the spinning turbines because backup power didn't kick in fast enough. In an attempt to test this scenario, several safety procedures were deliberately bypassed. Bad idea ... since the people doing the test were electricians .. not nuclear engineers. The result was no water being pumped into the reactor to cool it and no control rod deployment to shout it down. By the time the "kill switch" was hit, it was too late. An overheated core produced a feedback loop that accelerated the nuclear reactions. A steam explosion blew the top off the reactor .. and the plant was not designed with a containment vessel. Chernobyl is a ghost town now. The good news is this could not happen in any US nuclear power plant by engineering design and a completely different set of safety regulations.
Briefly explain what went wrong at the Fukushima nuclear power plant in 2011.

An earthquake struck off the coast of Japan on March 11, 2011. This was followed by a massive tsunami. Although the Fukushima plant had imitated shutdown procedures, multiple power backup systems all failed. This power was needed to run pumps to keep the core cool (even if control rods were in place).
In the last few decades, the US decreased its reliance on nuclear power to generate electricity. Can the opposite be said about any other nations? Explain.

Events at Three Mile Island, Chernobyl, and Fukushima have triggered a global reduction of the use of nuclear power. Look at this graph to see that following nuclear disasters, the world took notice and greatly reduced their reliance on nuclear power. The noticeable exception is China which has 27 new reactors under construction. There are also new reactors being built in South Korea, India, and Russia
What is the US currently doing with the radioactive wastes produced by nuclear power plants?

The answer is ... virtually nothing! In 2011, the US had over 72,000 tons of high-level nuclear waste with no long-term facility for storing it. Right now, these waste products are mainly kept "on site" in temporary storage. Most of the contamination at Fukushima came from leakage of spent fuel! Long range plans are to bury it deep in a geologically inactive and stable place. So where is that? .... and who would want that in their back yard? ... and how do you insure that it won't contaminate your ground water?

We should note that nuclear wastes encompasses a wide range of fission byproducts ... each with its own half life. Waste products with short half lives will safely decay quickly. It is the materials with long half lives that pose a big problem and are labeled High Level Wastes (HLW) ... these have half lives that measure in the millions of years range. Yikes!!!
What is a Liquid Fluoride Thorium Reactor? Are there any of these rectors currently in operation? What are the advantages of this type of nuclear reactor?

The details of this type of reactor were worked out in the 1960's but never implemented. Basically, thorium is used to make uranium 233 which then becomes the fuel in the reactor. Since it is liquid, the fuel itself is circulated and heat is transferred to a closed loop where steam drives a turbine. This reactor has several advantages over all traditional nuclear reactors. Thorium is abundant and all the waste products of this reactor have extremely short half lives when compared to currently used power plants. A core failure is virtually impossible (even if external power is cut off) since an overheated core will just melt a plug and the contents would drain into specially designed vessels. There is no need to use extremely high pressures, eliminating dangerous steam explosions. The only downside is this reactor needs to be kick started with traditional technologies. Why isn't this put into effect? Several nations are investigating this but public opinion on anything nuclear is currently a major deterrent.
How many nations currently have thermonuclear weapons? Which nation(s) or organizations do you feel pose the greatest threat to world peace with these devices?

There are currently nine nations with nuclear weapons. IMHO, the biggest threat comes not from any single nation (since releasing those weapons is akin to suicide), but from isolated radical groups who could manage to get their hands on some. The bombs need not be detonated, but used as ransom and/or to sabotage water systems (maybe I've just watched too many James Bond movies).
Are there currently any fusion reactors? What are some of the major obstacles in the quest for energy from fusion reactors. What is break-even? Has it been achieved?

Commercial fusion plants are decades away, but several reactors are in the research and testing phase. The problem is how do you confine hydrogen, get it to a superheated state, and stay that way after it fuses. There are several approaches .. mostly using lasers or magnetic forces. It is not easy containing a tiny hydrogen bomb. It takes a lot of energy to run all these devices so the first goal is to achieve break-even. That occurs when the energy you get OUT of the fusion reactor is equal to the energy you put IN. Scientists are very close to this major goal. I may have to change this answer any day.
Astronomers tell us the universe only consisted of hydrogen, helium, and lithium after the Big Bang. How do they account for the origin of all the other elements we see on the periodic table?

Theory predicts that you can fuse any element up to iron and release energy. The only problem is it takes higher temperatures and pressures each step you take (as you move toward iron). The only place nature currently produces these conditions is in the cores of very massive stars (much more massive than our sun). Our sun is converting hydrogen to helium but it doesn't have enough mass to do much more than that (except when it dies and flashes helium to carbon). Massive stars can synthesize all the elements up to iron BEFORE they die ... and when they die ... it is a spectacular event known as a supernova. When these stars blow up, there is so much energy available that some of it is used to fuse all the elements beyond iron on the periodic table (even though these reactions absorb energy). We know this because we can study the spectra of supernova remnants and identify these elements as they spew out into space. The real cool thing is this provides building blocks to make new star systems and worlds .. like Earth.
What are the dangers of a buildup of radon gas in your basement? How does it get there and how can the problem be eliminated?

The EPA predicts that up to 20,000 lung cancer deaths are the result of radon gas. There are two isotopes of this gas - radon-222, and radon-220 ... both radioactive. Radon 222 is the byproduct in the decay of Urnaium 238 and Radon 220 is the byproduct in the decay of thorium-232. Both uranium and thorium are elements found in nature so there is no way possible to avoid them. Because radon is a heavy inert gas, it is able to migrate from its place of origin and may settle in basements and wells. Radon emits alpha particles (the nucleus of helium atoms) which are dangerous to humans and animals if exposed to in high amounts.

The first step is to see if your basement hold unacceptable levels of radon gas. Home tests can be purchased at any home supply store for about $10. If you test positive for high radon levels, it will cost about $1,000 to have a ventilation system installed in your home.

Give one specific application where the radioactive properties of a material are put to use.

We are still receiving data from the Voyager probes which are well over 100 times further from the sun than the earth is. Voyager 1 & Voyager 2 were launched in 1977. The cameras are turned off but it still has enough power to transmit until the mid 2020's. At launch, both probes produced 470 w of 30 volt DC electrical power. To put this in layman's terms, this is the power output of a light bulb. However, since the power comes from the heat produced by the radioactive decay of Plutonium (that is attached to one junction of a thermocouple), the power levels have slowly dropped over time. This mandates that systems must be turned off, one-by-one, as the power levels drop.

This one could be big some day. How about a AAA battery that runs off the decay of radioactive nickel - 63? The prototype has 10 times the power of a standard chemical battery and would last much longer (the half life of nickel 63 is 100 years). Click here to read more.