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1. The word laser is short for       (7 words) .

2. The white light from an incandescent light bulb contains in it    (6 words); in an incandescent light bulb, the distances between the peaks of the waves, that is the  (1 word) change with the color.

3. When electrons absorb energy either from light (photons) or from heat (phonons), they move   (2 words) from the atomic nuclei but they are only allowed to absorb energy that will land them into specific energy levels. This leads to (3 words) lines.

An electromagnetic wave strikes an excited atom...        And the atom emits a new photon just like the first one.

 - (2 words) occurs when an electron decays on a lower energy level due to "timeout". When the excited atom decays into the ground state by this above defined process it releases the difference in energies between the two states as a  photon of     ν  (1 word) which has a certain     hν (1 word),  given by:

E₂ − E₁ = hν, where h is Planck's constant.

 -  (2 words) occurs when the already excited-state atom decays into the ground state by being perturbed by the electric field of a photon with frequency ν; the atom may release a second photon of the same frequency, in phase with the first photon.

4. The laser light is:

•   (1 word). It contains one specific wavelength of light (one specific color) which is determined by the amount of energy released when the electron drops to a lower orbit.
•   (1 word). It is “organized” -- each photon moves in step with the others. This means that all of the photons have wave fronts that launch in unison.
•  very   (1 word). A laser light has a very tight beam and is very strong and concentrated. A flashlight, on the other hand, releases light in many directions, and the light is very weak and diffuse.

5. A   (2 words) occurs when a group of atoms or molecules exists in state with more members in an  (2 words) than in  (2 words) states.

6. A laser consists of the parts explicitly labeled below. Explain the meaning of each following picture:

6a.

6b.

6c.

6d.

6e.

7. He-Ne Laser

The free electrons of the laser medium gain (2 words) from the strong electric field along the length of the tube, as they are accelerated toward the positive terminal. Before reaching the + terminal there is a   (1 word) probability that an energetic electron will collide with one of the many (2 words) and give it additional energy. This puts helium in an (2 words) as its electrons jump to higher energy levels. Each atom of excited helium located on the energy level happens to have the exact amount of energy that Neon requires before it will emit its red light. During the thermal motion of the excited helium atoms collisions occur with the (2 words)  in the laser tube. During this energy exchange the helium atom reverts to its (2 words)  and the Neon atom (1 word) just enough energy to raise one of its electrons to its level. At this metastable level, a neon electron can rest for a (2 words) before jumping back down toward ground level. There is a rather (1 word)  probability that an energetic electron can excite a neon atom directly to the desired level where laser action can occur because neon has electrons and many different excited levels for each..Although neon gas alone can provide some laser action, the laser effect is many times as great when it is mixed with a larger amount of helium in proportions of about .

8. Laser Applications

Briefly and concisely explain in the text areas below how each application works.

8a Laser Printer

a) The primary principle at work in a laser printer is (2 words). A laser printer uses this phenomenon as a sort of (2 words).

b) The core component of the laser printer system is the  (1 word), typically a revolving drum or cylinder which is made out of highly (1 word) material that is discharged by (2 words).

8b. Inside a CD player