Download light may 2011

Wave Nature of Light
Multiple Choice (Answer only 10 of the following)
Identify the choice that best completes the statement or answers the question.
____
1. Which of the following properties are common to water waves, sound waves, and light waves?
a. reflection only
b. refraction only
c. diffraction only
d. interference only
e. all of the above
____
2. Which of the following properties of light provides the strongest evidence that light is a wave rather than a
particle?
a. reflection
b. refraction
c. dispersion
d. diffraction
e. photoelectric effect
____
3. Which of the following might be a valid conclusion for the Young's double-slit experiment?
a. Light travels in a straight line.
b. Light is an electromechanical wave.
c. Collisions among light particles account for the interference pattern on the screen.
d. Light travels at a very high speed.
e. Light behaves as a wave in this experiment.
____
4. Which of the following is commonly used for heating and drying in industrial processes?
a. gamma rays
b. ultraviolet light
c. visible light
d. infrared light
e. microwaves
____
5. Which of the following is false?
a. Gamma rays can be used to study nuclear structure.
b. Gamma ray photons have more energy than X ray photons.
c. Gamma rays have higher frequency than radio waves.
d. Gamma rays are produced by electrons moving within atoms.
e. Gamma rays are the most penetrating electromagnetic waves.
____
6. A beam of vertically polarized light passes through a polarizer with virtually no changes. When a beam of
horizontally polarized light passes through the same polarizer, which of the following occurs?
a. No light is transmitted through the polarizer.
b. The light is transmitted, but becomes unpolarized.
c. The transmitted light becomes vertically polarized.
d. The light is partially reflected and partially transmitted.
e. none of the above
____
7. Which of the following continually emits electromagnetic waves?
a. insects
b. burning coal
c. humans
d. microwave ovens
e. all of the above
____
____
8. The time it takes for a wave to complete one cycle is called
a. period
b. frequency
c. wavelength
d. amplitude
9. Two identical waves which always interfere destructively must be out of phase by
a. 90o
b. 180o
c. 270o
d. 360o
____ 10. Visible light is produced by
a. electron ocillations through an antenna driven by electronic circuitry
b. high-frequency vibrations in small cavities
c. electron transitions in the atom
d. nuclear transformations
____ 11. Dispersion refers to
a. the bending of a wave around a corner
b. the monochromatic nature of light
c. the separation of white light into the visible spectrum
d. the bending of light when it changes mediums
____ 12. The frequency of the second hand on a clock is
a. 1/12 Hz
b. 12 hrs.
c. 1/60 Hz
d. 60 seconds
____ 13. How fast is the speed of light in km/hr
a. 3.0 x 108
b. 8.1 x 108
d. 1.1 x 109
c. 3.0 x 105
____ 14. Diffraction refers to
a. the bending of a wave around a corner
b. the monochromatic nature of light
c. the separation of white light into the visible spectrum
d. the bending of light when it changes mediums
Matching (7 marks)
Match the appropriate year with the scientist regarding the development fo our idea of light
a. Newton
e. Foucault
b. Michelson
f. Hertz
c. Snell
g. Young
d. Fresnel and Poisson
h. Aristotle
____ 15. 1621
____ 16. 1817
____ 17. 4th century BC
____ 18. 1704
____ 19. 1887
____ 20. 1905
____ 21. 1803
____ 22. 1850
a. Foucault
b. Newton
c. Hooke
d. Michelson
e. Fresnel and Poisson
f. Maxwell
____ 23. Corpuscular theory of light
____ 24. developed equations to show that light is an electromagnetic wave
____ 25. developed wave equations for diffraction which were verified by a bright spot at the centre of a shadow
____ 26. opposed Newton’s theory of light and supported Huygen’s wave model
____ 27. determine that the speed of light is less in water then air
____ 28. accurately measured the speed of light in 1905
Short Answer
Constants
Mass
Moon = 7.35 x 1022 kg
Earth = 5.98 x 1024 kg
electron = 9.11 x 10-31 kg
proton = 1.67 x 10-27 kg
neutron = 1.68 x 10-27 kg
sun = 1.99 x 1030 kg
Distances
Moon’s radius = 1738 km
Earth - Sun = 1.5 x 1011 m
Earth’s radius = 6.37 x 106 m
Earth - moon = 3.82 x 108 m
Constants
G = 6.67 x 10-11 Nm2/kg2
uair = 4 x 10-7 Tm/A
k = 9.0 x 109 Nm2/C2
h = 6.626 x 10-34 Js
c = 3.00 x 108 m/s
1 u = 1.661 x 10-27 kg
1 u = 931.5 MeV/c2
Charges
electron = -1.6 x 10-19 C
proton = 1.6 x 10-19 C
Senior Physics formulas
29. Explain how polarized sunglasses reduce glare. (3 marks)
30. Monochromatic light passes through a single slit, 0.400 mm wide, and shines on a screen 1.6 m away. If the
distance from the centre of the pattern to the first dark band is 2.0 mm, what is the wavelength of the light? (4
marks)
31. The separation between two slits is 1.75  105 and a screen is 0.56 m from the slits. Monochromatic violet
light with a wavelength of 4.30  107 passes through the slits. (6 marks)
a) How far from the central band will the first bright band appear on the screen?
b) What is the separation between successive bright bands?
c) What is the separation between successive dark bands?
d) How far from the central band will the tenth bright band appear on the screen?
e) What is the separation between the first and tenth bright bands?
32. a) Why does diffraction suggest that the particle theory of light is not entirely correct? (6 marks)
b) Describe the theory that explains diffraction.
c) What experiment first measured wavelengths of light?
Wave Nature of Light
Answer Section
MULTIPLE CHOICE
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
E
D
E
D
D
A
E
A
B
C
C
C
D
A
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
1
1
1
1
1
1
1
1
1
1
1
1
1
1
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
easy
easy
average
average
average
difficult
average
REF:
REF:
REF:
REF:
REF:
REF:
REF:
K/U
K/U
K/U
K/U
K/U
K/U
K/U
MATCHING
15.
16.
17.
18.
19.
20.
21.
22.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
C
D
H
A
F
B
G
E
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
1
1
1
1
1
1
1
1
23.
24.
25.
26.
27.
28.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
B
F
E
C
A
D
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
1
1
1
1
1
1
SHORT ANSWER
29. ANS:
When light strikes a surface such as a street or pool of water, the reflected light is horizontally polarized. The
polarized lenses in sunglasses are oriented to block the transmission of horizontally polarized light.
PTS: 1
DIF: average
REF: K/U | C
30. ANS:
PTS: 1
DIF: average
REF: K/U
PROBLEM
31. ANS:
a)
b)
c)
d)
e)
From part (a), bright bands are separated by 1.4 cm.
Dark bands are separated by the same distance as bright bands, which is 1.4 cm.
The tenth bright band is a distance of 10  1.4 cm = 14 cm from the central band.
The distance between the first and tenth bright bands is 9  1.4 cm = 13 cm.
PTS: 1
DIF: average
REF: K/U
32. ANS:
a) When light passes the edges of an opening, it bends and spreads behind the barrier. This phenomenon is
called “diffraction.” If the width of the opening is equal to the wavelength of the light, the angle of
deviation is 90. It is difficult to explain the “cancellation” of the initial velocity by particle theory.
b) In wave theory, the wavefronts from a source form wavelets as the secondary sources, which further emit
light in any direction. The wave theory worked better to explain diffraction.
c) The double-slit experiment allowed precise measurement of light's wavelength, using diffraction. Huygens'
wave theory, which was proposed in 1680 but later dropped, was revived after Thomas Young's double-slit
experiments in 1801.
PTS: 1
DIF: average
REF: C