Question 1

In the two-slit experiment, monochromatic light of frequency 5.00 × 1014 Hz passes through a pair of slits separated by 2.20 × 10^-5m. (c = 3.00 × 10⁸ m/s) (a) At what angle away from the central bright spot does the third bright fringe past the central bright spot occur? (b) At what angle does the second dark fringe occur?

Accepted Answer

(a) 4.69° 
(b) 2.34°

Question 2

Light of wavelength 519 nm passes through two slits. In the interference pattern on a screen 4.6 m away, adjacent bright fringes are separated by 5.2 mm in the general vicinity of the center of the pattern. What is the separation of the two slits?

Accepted Answer

0.46 mm

Question 3

Light from a monochromatic source shines through a double slit onto a screen 5.00 m away. The slits are 0.180 mm apart. The dark bands on the screen are measured to be 1.70 cm apart. What is the wavelength of the incident light?

Accepted Answer

A)   457 nm
B)   306 nm
C)   392 nm
D)   612 nm
E)   784 nm D

Question 4

Light of wavelength 525 nm passes through two slits separated by 0.500 mm and produces an interference pattern on a screen 7.80 m away. The intensity at the central maximum is I₀. What is the distance on the screen from the center of this central maximum to the point where the intensity due to double-slit interference has fallen to 1/2 I₀?

Accepted Answer

The answer of Light of wavelength 525 nm passes through...

Question 5

Two small forward-facing speakers are 2.50 m apart. They are both emitting, in phase with each other, a sound of frequency 1100 Hz in a room where the speed of sound is 344 m/s. A woman is standing opposite the midpoint between the speakers and is initially 35.0 m from the midpoint. As she slowly walks parallel to the line connecting the speakers, at what angle θ (relative to the centerline coming outward from the midpoint between the speakers) will she first hear no sound?

Accepted Answer

A)   0.063°
B)   3.6°
C)   7.2°
D)   1.8°
E)   11°

Question 6

In a double slit experiment, if the separation between the two slits is 0.050 mm and the distance from the slits to a screen is 2.5 m, find the spacing between the first-order and second-order bright fringes when coherent light of wavelength 600 nm illuminates the slits.

Accepted Answer

A)   1.5 cm
B)   3.0 cm
C)   4.5 cm
D)   6.0 cm
E)   9.0 cm

Question 7

Two radio antennas are 120 m apart on a north-south line, and they radiate in phase at a frequency of 3.4 MHz. All radio measurements are made far from the antennas. If the east-west reference line passes midway between the two antennas, what is the smallest angle from the antennas, measured north of east, at which constructive interference of two radio waves occurs? (c = 3.00 × 108 m/s)

Accepted Answer

A)   43°
B)   22°
C)   68°
D)   47°
E)   30°

Question 8

Coherent monochromatic light of wavelength 632.8 nm passes through a pair of thin parallel slits. The figure shows the central portion of the pattern of bright fringes viewed on a screen 1.40 m beyond the slits. What is the distance between the two slits?

Accepted Answer

A)   0.0703 mm
B)   0.141 mm
C)   0.281 mm
D)   0.562 mm
E)   0.633 mm

Question 9

A 360-nm thick oil film floats on the surface of the water. The indices of refraction of the oil and the water are 1.5 and 1.33, respectively. The surface of the oil is illuminated from above at normal incidence with white light. What TWO wavelengths of light in the 400-nm to 800-nm wavelength band are most strongly reflected?

Accepted Answer

A)   410 nm and 700 nm
B)   430 nm and 720 nm
C)   450 nm and 740 nm
D)   470 nm and 760 nm
E)   490 nm and 780 nm

Question 10

In a double-slit experiment, if the slit separation is increased, which of the following happens to the interference pattern shown on the screen?

Accepted Answer

A)   The minima get closer together.
B)   The maxima stay at the same position.
C)   The minima and maxima stay at the same position.
D)   The minima stay at the same position.
E)   The maxima get further apart.

Question 11

Light of frequency 6.00 × 1014 Hz illuminates a soap film (n = 1.33) having air on both sides of it. When viewing the film by reflected light, what is the minimum thickness of the film that will give an interference maximum when the light is incident normally on it? (c = 3.00 × 108 m/s)

Accepted Answer

A)   24.0 nm
B)   94.0 nm
C)   188 nm
D)   279 nm
E)   376 nm

Question 12

A coating is being applied to reduce the reflectivity of a pane of glass to light with a frequency of 5.75 × 1014 Hz that is incident normally on the pane. If the material has an index of refraction of 1.375 and the glass has an index of refraction of 1.537, what is the minimum thickness the coating should have? (c = 3.00 × 108 m/s)

Accepted Answer

A)   60.0 nm
B)   94.9 nm
C)   145 nm
D)   65.2 nm
E)   80.1 nm

Question 13

Two sources of light illuminate a double slit simultaneously. One has wavelength 570 nm and the second has an unknown wavelength. The m = 5 bright fringe of the unknown wavelength overlaps the m = 4 bright fringe of the light of 570 nm wavelength. What is the unknown wavelength?

Accepted Answer

A)   456 nm
B)   326 nm
C)   380 nm
D)   713 nm

Question 14

At most, how many bright fringes can be formed on each side of the central bright fringe (not counting the central bright fringe) when light of 625 nm falls on a double slit whose spacing is 1.97 × 10-6 m?

Accepted Answer

A)   1
B)   2
C)   3
D)   4
E)   5

Question 15

A double slit illuminated with light of wavelength 588 nm forms a diffraction pattern on a screen 11.0 cm away. The slit separation is 2464 nm. What is the distance between the third and fourth bright fringes away from the central fringe?

Accepted Answer

A)   23.9 cm
B)   5.96 cm
C)   5.59 cm
D)   2.63 cm

Question 16

A thin layer of oil (n = 1.25) is on top of a puddle of water (n = 1.33). If normally incident 500-nm light is strongly reflected, what is the minimum nonzero thickness of the oil layer?

Accepted Answer

A)   200 nm
B)   250 nm
C)   100 nm
D)   400 nm
E)   150 nm

Question 17

Two optically flat glass plates, 16.0 cm long, are in contact at one end and separated by 0.0200 mm at the other end. The space between the plates is occupied by oil with index of refraction 1.45. The index of refraction of the glass plates is 1.55. The plates are illuminated at normal incidence with monochromatic light, and fringes are observed. If the dark fringes are spaced 2.00 mm apart, what is the wavelength of the monochromatic light?

Accepted Answer

A)   425 nm
B)   475 nm
C)   525 nm
D)   675 nm
E)   725 nm

Question 18

A puddle of water has a thin film of gasoline floating on it. A beam of light is shining perpendicular on the film. If the wavelength of light incident on the film is 560 nm and the indices of refraction of gasoline and water are 1.40 and 1.33, respectively, what is the minimum thickness of the film to see a bright reflection?

Accepted Answer

A)   100 nm
B)   200 nm
C)   300 nm
D)   400 nm
E)   500 nm

Question 19

Monochromatic laser light of frequency 5.20 × 10¹⁴ Hz is shown on a pair of thin parallel slits, and the pattern is viewed on a screen 1.20 m away. The fifth bright fringes (not counting the central fringe) occur at ±2.12 cm on either side of the central bright fringe. The entire apparatus is now immersed in a transparent liquid. When the experiment is repeated, the fifth bright fringes now occur at ±1.43 cm from the central bright fringe. (c = 3.00 × 10⁸ m/s) (a) How far apart are the slits? (b) What is the index of refraction of the liquid?

Accepted Answer

The answer of Monochromatic laser light of frequency 5.20 ×...

Question 20

Light of wavelength 575 nm passes through a double-slit and the third order bright fringe is seen at an angle of 6.5° away from the central fringe. What is the separation between the double slits?

Accepted Answer

A)   5.0 µm
B)   10 µm
C)   15 µm
D)   20 µm
E)   25 µm

Exam 34: Interference