Question 1

You set two parallel slits 0.2 mm apart at a distance of 1 m from a screen and illuminate them with light of wavelength 400 nm. The distance between the first and second dark lines of the interference pattern on the screen is

Accepted Answer

A)  2.5 mm. 
B)  2.0 mm. 
C)  1.5 mm. 
D)  1.0 mm. 
E)  0.5 mm.

Question 2

You apply a material with n = 1.25 to a lens ng = 1.5) to make a nonreflective coating due to destructive interference at a wavelength in a vacuum) of 555 nm. What is the minimum thickness of the coating that you need?

Accepted Answer

A)  56 nm 
B)  110 nm 
C)  220 nm 
D)  280 nm 
E)  140 nm

Question 3

"To find the value of the resultant displacement for overlapping waves at any point at a particular instant, it is only necessary to add the values of the displacements for the individual waves." This is a statement of

Accepted Answer

A)  Huygens' principle. 
B)  the principle of superposition. 
C)  Bernoulli's principle. 
D)  the principle of dispersion. 
E)  Newton's theory of light.

Question 4

The different colors seen on a soap bubble are produced by

Accepted Answer

A)  the dispersion of light by the water in the soap. 
B)  the interference of light reflected from the front and back of the soap film. 
C)  the different angles light strikes the surface of the soap film. 
D)  total internal reflection of light in the soap film. 
E)  None of the statements is correct.

Question 5

You place a convex lens on top of a flat plate of glass and illuminate it with monochromatic light of wavelength 600 nm. You observe a dark circle at the center of the lens, surrounded by a series of concentric dark rings. What is the thickness of the air space between the lens and the flat glass plate where you see the sixth dark ring?

Accepted Answer

A)  3.90 µm 
B)  3.60 µm 
C)  1.80 µm 
D)  1.95 µm 
E)  2.10 µm

Question 6

Two side-by-side coherent light sources radiate at 633 nm. At a point in space where the path difference to these two sources is 30 nm, the phase difference could be

Accepted Answer

A)  0.238 radians. 
B)  0.298 radians. 
C)  0.324 radians. 
D)  0.356 radians. 
E)  0.429 radians.

Question 7

A ray of light is shown being reflected at the surface of a material. If the reflected ray is completely plane polarized, the index of refraction of the material is approximately

Accepted Answer

A)  1.3. 
B)  1.9. 
C)  0.63. 
D)  0.80. 
E)  1.8.

Question 8

A ray of light traveling in air enters the end of a rectangular block of a material that has an index of refraction n = 1.35. The largest value of the angle θ for which total internal reflection occurs at the upper surface of the material is approximately

Accepted Answer

A)  75º. 
B)  48º. 
C)  56º. 
D)  78º. 
E)  None of these is correct.

Question 9

A fiber optic is made by cladding a thin fiber core of refractive index n1 = 1.45 with a material of refractive index n2 = 1.38. What is the critical angle, Ɵc, at the core-cladding interface?

Accepted Answer

A)  44º 
B)  46º 
C)  55º 
D)  72º 
E)  None of these is correct.

Question 10

The plane of polarization of the reflected light lies

Accepted Answer

A)  parallel to the page. 
B)  at 45º with respect to the page. 
C)  at 34.6º with respect to the page. 
D)  at 55.4º with respect to the page. 
E)  perpendicular to the page.

Question 11

The minimum path difference that will produce a phase difference of 180º for light of wavelength 600 nm is

Accepted Answer

A)  600 nm. 
B)  500 nm. 
C)  300 nm. 
D)  200 nm. 
E)  100 nm.

Question 12

Two narrow slits, their centers separated by 15 cm, are illuminated by monochromatic radiation and produce the pattern in the figure on a distant screen. The wavelength of the radiation is

Accepted Answer

A)  0.52 cm. 
B)  1.0 cm. 
C)  1.6 cm. 
D)  2.1 cm. 
E)  3.0 cm.

Question 13

Why are fringes not observed if the angle of the wedge of air in the diagram is too large?

Accepted Answer

A)  For a large angle, the small-angle approximation sin θ ≈ θ) is not valid. 
B)  The light passing through the wedge of air loses its coherence. 
C)  The fringes overlap. 
D)  The fringes are too close together to be seen individually. 
E)  None of these is correct.

Question 14

Light of wavelength 500 nm illuminates parallel slits and produces an interference pattern on a screen that is 1 m from the slits. In terms of the initial intensity I0, the light's intensity in the interference pattern at a point for which the path difference is 300 nm is

Accepted Answer

A)  0.262 I0.  
B)  0.382 I0.  
C)  0.447 I0.  
D)  0.581 I0.  
E)  0.629 I0.

Question 15

Visible light from an ordinary source such as a sodium lamp can be used to produce interference effects that demonstrate the wave nature of light, provided that

Accepted Answer

A)  the light beam from the single source is split into two or more) beams that have a constant phase relationship to one another. 
B)  the light is polarized. 
C)  the light is not polarized. 
D)  Interference effects cannot be demonstrated with ordinary light sources. 
E)  None of these conditions are satisfied.

Question 16

A phase shift of 180º occurs when a light wave

Accepted Answer

A)  is transmitted through a boundary surface into a medium that is more dense than the medium from which the wave came. 
B)  is transmitted through a boundary surface into a medium that is less dense than the medium from which the wave came. 
C)  reflects from the boundary surface of a medium that is less dense than the medium in which the wave is traveling. 
D)  reflects from the boundary surface of a medium that is denser than the medium in which the wave is traveling. 
E)  Both c and d are correct.

Question 17

In order to produce several visible interference fringes from two narrow slits using light of a single wavelength, the distance between the slits must be of the order

Accepted Answer

A)  of a few tenths of the wavelength. 
B)  of a few wavelengths. 
C)  of a few tens wavelengths. 
D)  of a few hundreds wavelengths. 
E)  the distance does not matter.

Question 18

An object leaves point A and travels in a straight line to point B via path b. In region I, the speed is 100 m/s, while in region II, the speed is 71 m/s. How long does it take for the object to go from A to B?

Accepted Answer

A)  82.0 m/s 
B)  70.8 m/s 
C)  61.3 m/s 
D)  34.3 m/s 
E)  27.7 m/s

Question 19

In the figure, a beam of light from an underwater source is incident on a layer of carbon disulfide and the glass bottom of the container. Some of the refracted and reflected rays are shown in the diagram. For the rays shown, the interface at which the reflected light changes phase is

Accepted Answer

A)  1 only. 
B)  2 only. 
C)  3 only. 
D)  1 and 2. 
E)  2 and 3.

Question 20

A 60° prism has a refractive index of 1.64 for blue light and 1.61 for red light. Calculate the difference in the angle of emergence from the opposite face of the prism for a beam of red light and a beam of blue light that are both incident at an angle of 600.

Accepted Answer

A)  0.4° 
B)  0.0° 
C)  1.3° 
D)  3.9° 
E)  2.7°

Exam 23: Wave Properties of Light