Question 1

Two point sources, vibrating in phase, produce an interference pattern in a ripple tank. If the frequency is increased by 20%, the number of nodal lines:

Accepted Answer

A)  is increased by 20% 
B)  is increased by 40% 
C)  remains the same 
D)  is decreased by 20% 
E)  is decreased by 40% 
A)  is increased by 20% 
B)  is increased by 40% 
C)  remains the same 
D)  is decreased by 20% 
E)  is decreased by 40% A

Question 2

In an experiment to measure the wavelength of light using a double slit, it is found that the fringes are too close together to easily count them. To spread out the fringe pattern, one could:

Accepted Answer

A)  halve the slit separation 
B)  double the slit separation 
C)  double the width of each slit 
D)  halve the width of each slit 
E)  none of these 
A)  halve the slit separation 
B)  double the slit separation 
C)  double the width of each slit 
D)  halve the width of each slit 
E)  none of these A

Question 3

The light waves represented by the three rays shown in the diagram all have the same frequency. 4.7 wavelengths fit into layer 1, 3.2 wavelengths fit into layer 2, and 5.3 wavelengths fit into layer 3. Rank the layers according to the speeds of the waves, least to greatest.

Accepted Answer

A)  1, 2, 3 
B)  2, 1, 3 
C)  3, 1, 2 
D)  3, 2, 1 
E)  1, 3, 2 
A)  1, 2, 3 
B)  2, 1, 3 
C)  3, 1, 2 
D)  3, 2, 1 
E)  1, 3, 2 D

Question 4

A light wave with an electric field amplitude of 2E0 and a phase constant of zero is to be combined with one of the following waves. Which of these combinations produces the least intensity?

Accepted Answer

A)  wave A has an amplitude of E0 and a phase constant of zero 
B)  wave B has an amplitude of E0 and a phase constant of  $\pi$ 
C)  wave C has an amplitude of 2E0 and a phase constant of zero 
D)  wave D has an amplitude of 2E0 and a phase constant of  $\pi$ 
E)  wave E has an amplitude of 3E0 and a phase constant of  $\pi$ 
A)  wave A has an amplitude of E0 and a phase constant of zero 
B)  wave B has an amplitude of E0 and a phase constant of  $\pi$ 
C)  wave C has an amplitude of 2E0 and a phase constant of zero 
D)  wave D has an amplitude of 2E0 and a phase constant of  $\pi$ 
E)  wave E has an amplitude of 3E0 and a phase constant of  $\pi$

Question 5

Light from a small region of an ordinary incandescent bulb is passed through a yellow filter and then serves as the source for a Young's double-slit experiment. Which of the following changes would cause the interference pattern to be more closely spaced?

Accepted Answer

A)  Use slits that are closer together 
B)  Use a light source of lower intensity 
C)  Use a light source of higher intensity 
D)  Use a blue filter instead of a yellow filter 
E)  Move the light source further away from the slits 
A)  Use slits that are closer together 
B)  Use a light source of lower intensity 
C)  Use a light source of higher intensity 
D)  Use a blue filter instead of a yellow filter 
E)  Move the light source further away from the slits

Question 6

A liquid of refractive index n = 4/3 replaces the air between a fixed wedge formed from two glass plates as shown. As a result, the spacing between adjacent dark bands in the interference pattern:

Accepted Answer

A)  increases by a factor of 4/3 
B)  increases by a factor of 3 
C)  remains the same 
D)  decreases to 3/4 of its original value 
E)  decreases to 1/3 of its original value 
A)  increases by a factor of 4/3 
B)  increases by a factor of 3 
C)  remains the same 
D)  decreases to 3/4 of its original value 
E)  decreases to 1/3 of its original value

Question 7

Yellow light is viewed by reflection from a thin vertical soap film. Let $\lambda$ be the wavelength of the light within the film. Why is there a large dark space at the top of the film?

Accepted Answer

A)  no light is transmitted through this part of the film 
B)  the film thickness there is $\lambda$/4 
C)  the light reflected from exactly one of the two surfaces undergoes a 180 $\degree$ phase change 
D)  the film is too thick in this region for thin film formulas to apply 
E)  the reflected light is in the infrared 
A)  no light is transmitted through this part of the film 
B)  the film thickness there is $\lambda$/4 
C)  the light reflected from exactly one of the two surfaces undergoes a 180 $\degree$ phase change 
D)  the film is too thick in this region for thin film formulas to apply 
E)  the reflected light is in the infrared

Question 8

In a Young's double-slit experiment the center of a bright fringe occurs wherever waves from the slits differ in phase by a multiple of:

Accepted Answer

A)  $\pi$/4 
B)  $\pi$/2 
C)   $\pi$ 
D)  3 $\pi$/4 
E)  2 $\pi$ 
A)  $\pi$/4 
B)  $\pi$/2 
C)   $\pi$ 
D)  3 $\pi$/4 
E)  2 $\pi$

Question 9

Consider (I) the law of reflection and (II) the law of refraction. Huygens' principle can be used to derive:

Accepted Answer

A)  only I 
B)  only II 
C)  both I and II 
D)  neither I nor II 
E)  the question is meaningless because Huygen's principle is for wave fronts whereas both I and II concern rays 
A)  only I 
B)  only II 
C)  both I and II 
D)  neither I nor II 
E)  the question is meaningless because Huygen's principle is for wave fronts whereas both I and II concern rays

Question 10

To obtain an observable double-slit fringe pattern:

Accepted Answer

A)  the light must be incident normally on the slits 
B)  the light must be monochromatic 
C)  the light must consist of plane waves 
D)  the light must be coherent 
E)  the screen must be far away from the slits 
A)  the light must be incident normally on the slits 
B)  the light must be monochromatic 
C)  the light must consist of plane waves 
D)  the light must be coherent 
E)  the screen must be far away from the slits

Question 11

One of the two slits in a Young's experiment is painted over so that it transmits only one-half the intensity of the other slit. As a result:

Accepted Answer

A)  the fringe system disappears 
B)  the bright fringes get brighter and the dark ones get darker 
C)  the fringes just get dimmer 
D)  the dark fringes just get brighter 
E)  the dark fringes get brighter and the bright ones get darker 
A)  the fringe system disappears 
B)  the bright fringes get brighter and the dark ones get darker 
C)  the fringes just get dimmer 
D)  the dark fringes just get brighter 
E)  the dark fringes get brighter and the bright ones get darker

Question 12

An air wedge is formed using two glass plates that are in contact along their left edge. When viewed by highly monochromatic light, there are exactly 4001 dark bands in the reflected light. The air is now evacuated (with the glass plates remaining rigidly fixed) and the number of dark bands decreases to exactly 4000. The index of refraction of the air is:

Accepted Answer

A)  0.00025 
B)  0.00050 
C)  1.00025 
D)  1.00050 
E)  1.00000, by definition 
A)  0.00025 
B)  0.00050 
C)  1.00025 
D)  1.00050 
E)  1.00000, by definition

Question 13

Huygens' construction can be used only:

Accepted Answer

A)  for light 
B)  for an electromagnetic wave 
C)  if one of the media is vacuum (or air) 
D)  for transverse waves 
E)  for all of these and other situations 
A)  for light 
B)  for an electromagnetic wave 
C)  if one of the media is vacuum (or air) 
D)  for transverse waves 
E)  for all of these and other situations

Question 14

If two light waves are coherent:

Accepted Answer

A)  their amplitudes are the same 
B)  their frequencies are the same 
C)  their wavelengths are the same 
D)  their phase difference is constant 
E)  the difference in their frequencies is constant 
A)  their amplitudes are the same 
B)  their frequencies are the same 
C)  their wavelengths are the same 
D)  their phase difference is constant 
E)  the difference in their frequencies is constant

Question 15

A soap film is illuminated by white light normal to its surface. The index of refraction of the film is 1.50. Wavelengths of 480 nm and 800 nm and no wavelengths between are be intensefied in the reflected beam. The thickness of the film is:

Accepted Answer

A)  1.5* 10-5 cm 
B)  2.4 *10-5 cm 
C)  3.6 * 10-5 cm 
D)  4.0 * 10-5 cm 
E)  6.0 * 10-5 cm 
A)  1.5* 10-5 cm 
B)  2.4 *10-5 cm 
C)  3.6 * 10-5 cm 
D)  4.0 * 10-5 cm 
E)  6.0 * 10-5 cm

Question 16

Binoculars and microscopes are frequently made with coated optics by adding a thin layer of transparent material to the lens surface as shown. One wants:

Accepted Answer

A)  constructive interference between waves 1 and 2 
B)  destructive interference between waves 3 and 4 
C)  constructive interference between 3 and 4 
D)  the coating to be more transparent than the lens 
E)  the speed of light in the coating to be less than that in the lens 
A)  constructive interference between waves 1 and 2 
B)  destructive interference between waves 3 and 4 
C)  constructive interference between 3 and 4 
D)  the coating to be more transparent than the lens 
E)  the speed of light in the coating to be less than that in the lens

Question 17

In a Young's double-slit experiment, a thin sheet of mica is placed over one of the two slits. As a result, the center of the fringe pattern (on the screen) shifts by an amount corresponding to 30 dark bands. The wavelength of the light in this experiment is 480 nm and the index of the mica is 1.60. The mica thickness is:

Accepted Answer

A)  0.090 mm 
B)  0.012 mm 
C)  0.014 mm 
D)  0.024 mm 
E)  0.062 mm 
A)  0.090 mm 
B)  0.012 mm 
C)  0.014 mm 
D)  0.024 mm 
E)  0.062 mm

Question 18

In a Young's double-slit experiment, the separation between slits is d and the screen is a distance D from the slits. D is much greater than d and $\lambda$ is the wavelength of the light. The number of bright fringes per unit length on the screen is:

Accepted Answer

A)  Dd/$\lambda$ 
B)  D$\lambda$/d 
C)  D/d$\lambda$ 
D)  $\lambda$/Dd 
E)  d/D$\lambda$ 
A)  Dd/$\lambda$ 
B)  D$\lambda$/d 
C)  D/d$\lambda$ 
D)  $\lambda$/Dd 
E)  d/D$\lambda$

Question 19

In a Young's double-slit experiment, the slit separation is doubled. This results in:

Accepted Answer

A)  an increase in fringe intensity 
B)  a decrease in fringe intensity 
C)  a halving of the wavelength 
D)  a halving of the fringe spacing 
E)  a doubling of the fringe spacing 
A)  an increase in fringe intensity 
B)  a decrease in fringe intensity 
C)  a halving of the wavelength 
D)  a halving of the fringe spacing 
E)  a doubling of the fringe spacing

Question 20

In a Young's experiment, it is essential that the two beams:

Accepted Answer

A)  have exactly equal intensity 
B)  be exactly parallel 
C)  travel equal distances 
D)  come originally from the same source 
E)  be composed of a broad band of frequencies 
A)  have exactly equal intensity 
B)  be exactly parallel 
C)  travel equal distances 
D)  come originally from the same source 
E)  be composed of a broad band of frequencies

Exam 35: Interference

Two point sources, vibrating in phase, produce an interference pattern in a ripple tank. If the frequency is increased by 20%, the number of nodal lines:

In an experiment to measure the wavelength of light using a double slit, it is found that the fringes are too close together to easily count them. To spread out the fringe pattern, one could:

The light waves represented by the three rays shown in the diagram all have the same frequency. 4.7 wavelengths fit into layer 1, 3.2 wavelengths fit into layer 2, and 5.3 wavelengths fit into layer 3. Rank the layers according to the speeds of the waves, least to greatest.

A light wave with an electric field amplitude of 2E0 and a phase constant of zero is to be combined with one of the following waves. Which of these combinations produces the least intensity?

Light from a small region of an ordinary incandescent bulb is passed through a yellow filter and then serves as the source for a Young's double-slit experiment. Which of the following changes would cause the interference pattern to be more closely spaced?

A liquid of refractive index n = 4/3 replaces the air between a fixed wedge formed from two glass plates as shown. As a result, the spacing between adjacent dark bands in the interference pattern:

Yellow light is viewed by reflection from a thin vertical soap film. Let λ\lambdaλ be the wavelength of the light within the film. Why is there a large dark space at the top of the film?

In a Young's double-slit experiment the center of a bright fringe occurs wherever waves from the slits differ in phase by a multiple of:

Consider (I) the law of reflection and (II) the law of refraction. Huygens' principle can be used to derive:

To obtain an observable double-slit fringe pattern:

One of the two slits in a Young's experiment is painted over so that it transmits only one-half the intensity of the other slit. As a result:

Huygens' construction can be used only:

If two light waves are coherent:

A soap film is illuminated by white light normal to its surface. The index of refraction of the film is 1.50. Wavelengths of 480 nm and 800 nm and no wavelengths between are be intensefied in the reflected beam. The thickness of the film is:

Binoculars and microscopes are frequently made with coated optics by adding a thin layer of transparent material to the lens surface as shown. One wants:

In a Young's double-slit experiment, the separation between slits is d and the screen is a distance D from the slits. D is much greater than d and λ\lambdaλ is the wavelength of the light. The number of bright fringes per unit length on the screen is:

In a Young's double-slit experiment, the slit separation is doubled. This results in:

In a Young's experiment, it is essential that the two beams:

Measurement

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Filters

A light wave with an electric field amplitude of 2E₀ and a phase constant of zero is to be combined with one of the following waves. Which of these combinations produces the least intensity?

In a Young's double-slit experiment, the separation between slits is d and the screen is a distance D from the slits. D is much greater than d and $\lambda$ is the wavelength of the light. The number of bright fringes per unit length on the screen is: