 # Fourth Hour Exam

## April 28, 1998

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E) none of the above

Possibly useful information:

v = x / t p = m v T = 2  a = v / t PE = m g h T = 2  v = vi + a t PE = (1/2) k x2 v = x = xi + vi t + (1/2) a t2 KE = (1/2) m v2 v=(wavelength) x (frequency)

v = r  F = k x L = (n) x (half wavelength)

F = m a Ei = Ef

F12 = - F21 pi = pf

w = mg F = p / t

g = 9.8 m/s2 10 m/s2

1/f = 1/do + 1/di

M = - di/do

M = 25 cm/f

di = [1/n] do

n1 sin 1 = n 2 sin 2

M = fobj/feye

c = 3.00 x 108 m/s

For every question, also consider as a possible answer

E) none of the above

For every question, also consider the following as a possible answer:

e) none of the above

1. Electromagnetic waves consist of

a) compressions and rarefactions of electromagnetic pulses.

b) longitudinally polarized wave pulses.

c) oscillating electric and magnetic fields.

d) high-frequency gravitational waves.

2. Electromagnetic waves

a) can travel through a vacuum.

b) need a medium to travel through.

3. The main difference between a radio wave and a light wave is its

a) speed

b) EM characteristic

c) wavelength

d) all of the above

4. Which of these electromagnetic waves has the shortest wavelength?

a) X-rays

b) ultraviolet waves

c) infrared waves

5. Compared to ultraviolet waves, the wavelength of infrared is

a) longer

b) identical

c) shorter

6. Compared to radio waves, the wavelength of visible light waves in a vacuum is

a) longer

b) the same

c) shorter

7. Which of the following is fundamentally different from the others?

a) X-rays

b) visible light waves

c) sound waves

d) microwaves

8. The sensation of color is seen when light falls on the eye's

a) rods

b) cones

c) cornea

d) crystalline lens

9. The cones in the retina of the eye are

a) concentrated at the "blind spot" where the optic nerve attaches to the retina.

b) uniformly spread along the visual field.

c) concentrated along the periphery of vision.

d) most densely packed at the center of vision, the fovea.

10. Optical astronomers look at stars using the visible spectrum, with optical telescopes made of lenses or, more probably, mirrors. Radio astronomers look at stars using radio waves and very large "radio telescopes". Other than our own Sun, Alpha Centauri, is the closest star to Earth; it is a little over four light-years away.

If a light signal and a radio signal were emitted simultaneously from Alpha Centauri, the first signal to reach Earth would be the

b) light signal

c) both would arrive at the same time

11. Color depends on what characteristic of light?

a) wavelength

b) frequency

c) both of these

d) neither of these

12. The colored dots that make up the color on a TV screen are

a) red, yellow, green

b) red, yellow, blue

c) red, green, blue

d) cyan, magenta, yellow

13. Colors seen on TV result from color

a) subtraction

c) neither of these

d) either of these

14. Colors seen in paint result from color

a) subtraction

c) neither of these

d) either of these

15. Different colors of light correspond to different light

a) velocities

b) frequencies

c) polarities

d) intensities

16. Look at a full-color picture in a magazine with a magnifying glass and you will see that the inks used are

a) red, green, cyan, and blue.

b) red, green, blue, and black.

c) cyan, magenta, yellow, and black.

d) cyan, green, yellow, and blue.

17. A blue object will appear black when illuminated with

a) blue light

b) yellow light

c) red light

d) cyan light

18. A mixture of red and green light produces

a) blue

b) magenta

c) yellow

d) cyan

19. A spotlight produces white light which then passes through a filter that absorbs the red light. What color is the light that passes through?

a) red

b) yellow

c) magenta

d) cyan

20. Light travels fastest in

a) water

b) vacuum

c) air

d) glass

21. Light refracts when traveling from air into glass because light

a) intensity is greater in air than in glass

b) frequency is greater in glass than in air

c) speed is greater in air than in glass

d) polarization is greater in glass than in air

22. A beam of light emerges from water into air at an angle. The beam is bent

a) toward the normal

b) away from the normal

c) at an angle of 49°

d) only if it is polarized

23. When a light beam emerges from water into air, the light speed

a) increases

b) remains the same

c) decreases

24. Refraction causes the a fish in an acquarium to appear

a) farther away from the surface than it really is

b) closer to the surface than it really is

25. Different colors are dispersed by a prism because different colors in the spectrum have different

a) speeds

b) wavelengths

c) energies

d) momenta

26. The critical angle for a transparent material is the angle at and beyond which all light within the material is totally

a) absorbed

b) reflected

c) refracted

d) polarized

27. In an optical fiber, light actually

a) curves in a direction parallel to the central axis of the fiber.

b) travels in straight-line segments.

c) travels along the outer surface of the fiber.

d) all of the above.

28. Your image in a plane mirror is

a) virtual

b) real

c) both of these

29. The type of lens that brings parallel light down to a point (or "focuses" the parallel light to a point is a a) converging lens

b) diverging lens

c) either of these

30. Which of the following can be projected onto a viewing screen?

a) a real image

b) a virtual image

c) a convex image

d) a concave image

31. The image of something "infinitely far away", like the Sun, produced by a converging lens appears

a) between the lens and the focal point

b) at the focal point

c) between the focal point and twice the focal length

d) at twice the focal length

32. Your vision is sharpest

a) along the outer edge of the retina.

b) when your pupil is constricted or made tiny

c) where the optic nerve connects to the retina

d) when your pupil is dilated or opened wide

33. Consider plane waves incident upon a barrier with a small opening. After passing through the opening, the waves

a) continue as plane waves

c) are polarized

d) converge

34. Light will not pass through a pair of Polaroid filters when their axes are

a) parallel

b) rotated 45°

c) rotated 57°

d) perpendicular

35. Monochromatic light is light of a single

a) color

b) wavelength

c) frequency

d) all of the above

36. Light from a laser is

a) monochromatic

b) in phase

c) coherent

d) all of the above

37. A 2-m tall person viewing his full-length image in a plane mirror requires a mirror that is at least

 a) 0.5 m b) 1.0 m. c) 2.0 m. d) Twice the person's distance from the mirror. 38. Rainbows are a result of

a) dispersion and reflection.

b) dispersion and polarization.

c) reconstruction and polarization.

d) constructive and destructive interference.

39. An object is placed 20 cm from a converging lens that has a focal length of 10 cm. Make a ray diagram of this situation. From the ray diagram, characterize the image. The image is

a) real and inverted (and the same size)

b) virtual, inverted, and smaller.

c) virtual, upright, and smaller.

d) virtual, inverted, and larger.

40. An object is placed 30 cm from a converging lens that has a focal length of 10 cm. Make a ray diagram of this situation. From the ray diagram, characterize the image. The image is

a) real, inverted, and larger.

b) real, inverted, and smaller.

c) virtual, upright, and smaller.

d) virtual, inverted, and smaller.

41. An object is placed 15 cm from a converging lens that has a focal length of 10 cm. Make a ray diagram of this situation. From the ray diagram, characterize the image. The image is

a) real, inverted, and larger.

b) real, inverted, and smaller.

c) real, upright, and smaller.

d) virtual, upright, and larger.

42. An object is placed 5 cm from a converging lens that has a focal length of 10 cm. Make a ray diagram of this situation. From the ray diagram, characterize the image. The image is

a) real, inverted, and larger.

b) real, inverted, and smaller.

c) virtual, upright, and smaller.

d) virtual, upright, and larger.

43. The "near point" of a farsighted person is

a) 25 cm

b) the nearest distance at which that person can clearly see an object

c) twice the focal length of that person's corrective lenses

d) just longer than the person's arms

44. The type of lenses needed to correct farsighted vision is a) converging

b) diverging

c) convex

d) concave

45. A simple magnifier produces a virtual image

a) a virtual image between the lens and your eye

b) a real image between the lens and your eye

c) a virtual image beyond the near point of your eye

d) a real image at infinity

46. An eyepiece is a

a) diverging lens used to make an upside down image right side up

b) diverging lens used to produce a real image

c) converging lens used as a simple magnifier

d) converging lens used to make an upside down image right side up

47. A telescope uses the front lens or objective lens to produce a

a) virtual image which is right side up.

b) virtual image at infinity.

c) real image which is then viewed through the eyepiece.

d) real image which is right side up.

48. In the interference pattern produced by shining a laser through two slits (Young's double slit experiment), the dark areas are the result of

a) destructive interference.

b) polarization.

c) constructive interference.

d) restructive construction.

49. When light passes through a diffraction grating it is bent. Light with a greater wavelength will be bent

a) through a smaller angle.

b) the same (bending is independent of wavelength).

c) through a larger angle.

50. In the spectra produced from a white light source by a diffraction grating,

a) yellow is on the inside of the spectra and green is on the outside

b) green is on the inside of the spectra and yellow is on the outside

c) red is on the inside of the spectra and violet is on the outside

d) violet is on the inside of the spectra and red is on the outside

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