Choose the best possible answer for each question.
Closed book exam. No notes or help of any kind allowed.
Please submit your answers by email to ral5q@virginia.edu.

1. A fluorescent light has mercury vapor in the tube that emits ultraviolet light when the atoms collide due to the applied voltage that accelerates the electrons and ions. The visible light that you see is produced by

   (A) re-emission of light by the phosphor on the inside of the bulb after absorption of the ultraviolet.
   (B) light directly emitted by the mercury vapor atoms when they collide with the phosphor.
   (C) light from accelerated phosphor atoms due to the applied voltage.
   (D) radiation from electrons accelerated by the applied voltage.

2. More highly curved lenses will create an image that is

   (A) smaller and brighter than a lens with less curvature.
   (B) smaller and dimmer than a lens with less curvature.
   (C) larger and dimmer than a lens with less curvature.
   (D) larger and brighter than a lens with less curvature.

3. An incandescent lightbulb converts electrical energy to visible light energy at the level of about

   (A) 10%.
   (B) 90%.
   (C) 0.1%.
   (D) none of the above

4. In an atom like neon the electron travels around the nucleus in different orbits and when the electron changes from a higher energy orbit to a lower energy orbit, it emits radiation in the form of light. The neon light is mostly red because

   (A) the glass tube has a red coating.
   (B) the wavelength of the electron is the same as red light.
   (C) it is similar to the incandescent light bulb.
   (D) the energy change of the electron is carried away by the red light .

5. You are observing a distant ship with a telescope but all you can see and read is the ship's name. To decrease the magnification of the telescope, so you can see more of the ship you replace the current eyepiece with one that

   (A) has a larger aperture (larger diameter).
   (B) contains a less highly curved lens (a longer focal length).
   (C) has a smaller aperture (smaller diameter).
   (D) contains a more highly curved lens (a smaller focal length).

6. A compact disc player or CD reproduces sound at a very high level of fidelity because:

   (A) the sound is digitized and recorded on the CD as an array of little permanent magnets.
   (B) the sound is digitized and recorded on the CD as an array of charged capacitors.
   (C) the sound is digitized and recorded on the CD as an array of little inductors.
   (D) the sound is digitized and recorded on the CD as an array of ridges and gaps.

7. The Pauli Exclusion principle states that

   (A) only two electrons can be in the same orbit if both have spin up, but orbiting in opposite directions.
   (B) only two electrons can be in the same orbit if both have spin down, but orbiting in opposite directions.
   (C) only two electrons can be in the same orbit if each has no spin.
   (D) only two electrons can be in the same orbit if one electron has spin up and one has spin down.

8. In order to improve the depth of field of your camera so that you can get a clear image of objects at different distances from the camera, you have to

   (A) increase the size of the aperture to let more light into the camera.
   (B) decrease the size of the aperture.
   (C) increase the speed of the camera while you increase the size of the aperture to let more light into the camera.
   (D) none of the above will do it.

9. An engineer at the company you're working for has just reported finding an unusual electromagnetic wave. This wave consists only of an electric field, with no magnetic field accompanying it. You are certain that the engineer is mistaken because

   (A) electromagnetic waves contain moving electric charges and charges produce magnetic fields when they move.
   (B) while waves consisting only of electric fields are common and travel indefinitely through space, they are known as "electric waves," not "electromagnetic waves."
   (C) an electromagnetic wave must have a magnetic field that changes with time to produce its electric field.
   (D) electromagnetic waves always contain both electric charges and magnetic poles, and magnetic poles are accompanied by magnetic fields.

10. In a typical red laser, the light bounces back and forth between two mirrors and is amplified by the excited atoms in the laser medium. However, you cannot see the laser light from the side when it travels through air. If you allow the laser light to go through smoke or water vapor you can see the laser light from the side. This is caused by

    (A) the magnetic field of the laser light exciting the water molecules and then re-emitting the light in all directions, but of the same wavelength.
    (B) the electric field of the laser light exciting the water molecules and then re-emitting the light as a laser beam in one direction.
    (C) the electric field of the laser light exciting the water molecules and then re-emitting the light in all directions but of the same wavelength.
    (D) none of the above.

11. A flat mirror produces a virtual image no matter where the object is placed. A convex lens produces a virtual image if the object is too close to the lens. The virtual image has the property that

    (A) the actual light rays do not pass through the image.
    (B) the actual light rays do pass through the image.
    (C) the actual light rays cannot be focused by a lens to form a real image.
    (D) the actual light rays can be focused but only into another virtual image.

12. The purpose of a ballast in a fluorescent lamp is to

    (A) act as a capacitor to accelerate ionized atoms to start electrons flowing.
    (B) act as an inductor to prevent current from being excessive.
    (C) act as an inductor to keep current flowing reducing overall power.
    (D) act as a capacitor to store charge to prevent current from being excessive.

13. If a 60 Hz sinusoidal varying strong magnetic field is held up close to a color TV screen,

    (A) it will permanently magnetize the phosphor and no images will be discernible.
    (B) it will distort the images, but they will be discernible.
    (C) images will not be distorted, but the color will be unrealistic.
    (D) images will not be distorted and color will be normal.

14. An electromagnetic wave is not created when

    (A) an electric charge is moving at a constant velocity in a wire.
    (B) an electric charge is moving at a varying velocity in a wire.
    (C) an electric charge is moving in a circle in a vacuum at a fixed speed.
    (D) an electric charge is accelerating through space.

15. When you put a normal CD in a microwave oven and turn the oven on,

    (A) the CD melts slowly.
    (B) the microwave oven immediately burns out because the CD contains metal and metals damage microwave ovens.
    (C) nothing happens because the CD contains no water to absorb the microwaves.
    (D) the CD glows and emits sparks.

16. As the current increases by a large amount through the filament of an incandescent light bulb, the color of the filament most likely will go from

    (A) red to orange to blue.
    (B) red to blue to orange.
    (C) orange to blue to red.
    (D) blue to orange to red.

17. A hungry UVa teacher in RECET attempts to microwave a frozen burrito. The teacher discovers that part of it gets hot and soft , but part of it is also cold and still frozen. This is because

    (A) the polar water molecules are depolarized and no longer absorb the microwaves.
    (B) the polar water molecules in the frozen stage cannot move.
    (C) there are not enough polar water molecules.
    (D) none of the above

18. Consider a fiber optic cable and a standard coaxial cable which are used to transmit television signals. Which of the following is true?

    (A) Co-axial cable will give you a clearer picture than a fiber optic cable because no light gets in the co-axial cable.
    (B) Co-axial cable gives about 170 channels and the fiber optic cable can in principle give up to 50 million channels.
    (C) Co-axial cable gives about 170 channels and the optic cable can in principle give up to 50 thousand channels.
    (D) A TV channel can transmit every 3 MegaHertz in the fiber optic cable.

19. One advantage of using an enormous mirror to collect light in a telescope is that the real image is relatively bright. These large mirrors give us the best possible resolving power to separate two distant stars. Having the Hubble Space Telescope in outer space improves our ability to separate distant stars because

    (A) the telescope is closer to the stars.
    (B) the mirrors are even bigger because we dont have to worry about wind effects.
    (C) atmospheric effects due to changes in the speed of light are eliminated.
    (D) atmospheric effects due to changes in the frequencies of light are eliminated.

20. An electron microscope is an example of a non-optical microscope. It can be used to measure the distance between atoms. The microscope is based on

    (A) the point-like nature of the electron.
    (B) the wave-like nature of the electron at sufficiently high electron energies.
    (C) the electron producing visible light while being accelerated.
    (D) none of the above.
    

21. The sky is blue and sunsets are red because

    (A) shorter wavelengths of light are scattered more then longer wavelengths by small particles in the air.
    (B) shorter wavelengths of light are scattered less then longer wavelengths by small particles in the air.
    (C) shorter wavelengths of light are scattered more then longer wavelengths by the water molecules in the clouds.
    (D) shorter wavelengths of light are scattered less then longer wavelengths by ionized particles in the air.

22. A reflecting telescope has the advantage that its main optic has only one element (a curved mirror) and that this element doesn't have to be made of transparent material. In contrast, the simplest high-quality refracting telescope needs two elements in its main optic (a converging lens) and both elements must be perfectly transparent. It needs these two transparent elements in its lens because a single element lens

    (A) can't bring all the colors to a focus at the same distance.
    (B) can only form a virtual image and not a real image.
    (C) causes light to spread apart rather than come together.
    (D) will produce an inverted real image while a two element lens will produce an upright real image.

23. The colors in the rainbow and soap bubbles are due to

    (A) refraction and reflection of light in the water droplet and refraction and reflection in the soap bubble.
    (B) refraction in the water droplet and refraction and interference in the soap bubble.
    (C) refraction and reflection in the water droplet and refraction, reflection and interference in the soap bubble.
    (D) refraction, reflection, and interference in the water droplet and refraction, reflection and interference in the soap bubble.

24. A lens has a focal length of 10 centimeters and the object is at the end of a football field about 100 meterslong. The image is formed at about what distance from the lens?

    (A) 5 cm
    (B) 20 cm
    (C) 10000 cm
    (D) 10 cm
    

25. Red eye in a photograph is caused by the camera flash illuminating the blood on your retina (lens in your eye acts as a camera) and then the lens in your eye projects it back into the camera on to the photograph. It can be reduced by

    (A) decreasing the f-number.
    (B) increasing the shutter speed.
    (C) decreasing the shutter speed.
    (D) firing the flash twice or more.