Diffraction I PREFLIGHT
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1.

Double Slit Diffraction

You can drag the red wall, and simultaneously adjust the distance between the two slits. Put the slits together and you have a single slit. Its a little awkward, but I found I can move the wall, and then adjust the slits.
a) What can you say about the "single slit" pattern?
b) Classically, the double slits should produce an image of two slits on the wall. What must you do to make it look "Classical"?
c) Why should moving the red wall make a difference on the blue intensity pattern?




2.

Suppose that you are taking data in the lab, and your job is to say whether two bacteria, stained green with fluorescent dye, are moving toward each other or away from each other when you play rock music. The problem is that the bacteria are awfully small, and you can just barely tell them apart. You want to see them better, and you suspect that it has to do with your eyes. Should you:

Turn out the room lights to make the bacteria appear brighter.

Turn on the room lights to make the bacteria show up better.

Eat some carrots, and rest your eyes before taking data.

Hyperventilate and use the vision off to the side of line of sight.

3.

Integrated circuit manufacturers, such as Intel, make computer chips with a machine called a "Stepper". See http://www.asml.com/profile/life98.htm It shines an ultraviolet light through a "mask" which exposes a wafer of silicon coated with a special polymer. Wherever the light falls on the polymer, it "cures" it, and makes it hard. Then the unexposed polymer is washed off, and the silicon wafer dipped in an acid that etches or removes the uncoated silicon. Many such steps produce a microchip. The big thing in microchips is making everything smaller, so that it uses less electricity and runs faster. If the UV light has a wavelength of 200 nm in this stepper, what is the smallest feature, say, a wire that can be constructed with this approach?



honors extra

In 1957, President Eisenhower was told by his military intelligence that the Russians had a huge number of missiles capable of destroying American cities with nuclear bombs. The military wanted a big budget increase to start building ICBMs to remedy the "missile gap". Eisenhower, despite being a former general, distrusted the group of people he christened the "military industrial complex". He wanted proof of a missile gap. Unfortunately, the U2 spyplane was shot down in Russia, and the US was unable to take photos. The satellite program was in its infancy when Eisenhower commissioned a study to determine how we could monitor Russian air bases from space. Two proposals were presented, one suggested flying a TV camera with a vidicon tube, the other proposal suggested flying a camera and dropping the film back to earth. Eisenhower went with the second proposal in 1958, code named "CORONA". One failure followed another, and it was almost 2 years later in 1960, after 13 failed missions that the US retrieved its first film capsule. See http://observe.ivv.nasa.gov/nasa/exhibits/spy/spy_3.html As Eisenhower had feared, the film confirmed his suspicions that there was no missile gap. Eisenhower's greatness, in my mind, follows the example of all other great presidents and world leaders. When he knew something was right, he never gave up, but persevered through every adversity. Why did Eisenhower know that a film camera was needed, even though it was so difficult to get the film back?




Below is a space for your thoughts, including general comments about today's assignment (what seemed impossible, what reading didn't make sense, what we should spend class time on, what was "cool", etc.):




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I received no help from anyone on this assignment.