UNIT 4: THE WAVE NATURE OF LIGHT
UNIT TEST
NAME:
TOTAL MARKS:
MULTIPLE CHOICE QUESTIONS
/25
10 MARKS
Circle the best answer:
1. Polarization of light cannot be achieved in one of the following ways:
a) Reflection
b) Polarizing filter
c) Interference
d) Double refraction
e) Scattering
2. In Young’s double slit experiment the slit separation is made 3-fold. The fringe
width will
a) 1/3 times.
b) 3/5 times.
c) 3 times.
d) 9 times.
3. If the sodium light in young’s double slit experiment is replaced by red light, the
fringe width will
a) Decrease
b) Increase
c) Remain unaffected
d) First increase and then decrease.
4. Two small light bulbs are placed close together to try and create an interference
pattern. The pattern would not be visible due to
a) Random phase difference between the light waves from the two sources.
b) Very high speed of light waves.
c) Diffraction of light through air molecules surrounding the bulbs.
d) Very short wavelengths of the light waves.
e) Inability of the human eyes to resolve two sources close together.
5. The colours in anti-reflective coatings on eyeglasses, solar cells, and the colours
seen as sunlight shines on a soap bubble, can be explained by
a) Light interfering as it reflects within a thin film.
b) Light diffracting within a thin film.
c) Light dispersing across a thick film.
d) Light polarizing inside a thin film.
6. Two identical waves which always interfere destructively must be out of phase
by
a) 90°
b) 180°
c) 270°
d) 360°
7. Calculate the speed of light in diamond (n = 2.42)
a) 1.24 x 108 m/s
b) 7.26 x 108 m/s
c) 1.24 x 107 m/s
d) 7.26 x 107 m/s
8. Monochromatic light from a point source projected on an opaque screen with
two parallel slits spaced 2.5 x 10−5 meters apart has a first order bright fringe
that is 1.7° from the center. What is the wavelength?
a) 530 nm
b) 610 nm
c) 640 nm
d) 690 nm
e) 740 nm
9. The spectrum of light produced by a prism when white light travels through it is
caused by:
a) Making the ultraviolet and infrared wavelengths visible.
b) The bending of each wavelength of visible light through a slightly different
angle.
c) The diffraction of light by an obstacle.
d) A total internal reflection within the prism.
10. Of the five figures below, choose the one which most accurately illustrates single
slit diffraction from a monochromatic source.
PROBLEMS:
1. Sodium vapour light with an average wavelength of 589 nm falls on a single slit,
7.5 x 10−6 m wide. Calculate
a) At what angle is the second minimum?
2 MARKS
b) What is the highest order minimum produced.
3 MARKS
2. A two point interference pattern in a water tank is formed by waves moving at 4.0
cm/s. A point on the third nodal line is located 22.0 from one source and 15.5 cm
from the other source. Find the wavelength and the frequency of waves.
5 MARKS
EXTENDED RESPONSE
5 MARKS
1. Radio waves and light waves are both electromagnetic waves but radio waves
diffract prominently around buildings, while light waves do not. Why?
ANSWERS
1. Polarization of light cannot be achieved in one of the following ways:
f)
g)
h)
i)
j)
Reflection
Polarizing filter
Interference
Double refraction
Scattering
2. In Young’s double slit experiment the slit separation is made 3-fold. The fringe width will
e)
f)
g)
h)
1/3 times.
3/5 times.
3 times.
9 times.
3. If the sodium light in young’s double slit experiment is replaced by red light, the
fringe width will
e) Decrease
f) Increase
g) Remain unaffected
h) First increase and then decrease.
4. Two small light bulbs are placed close together to try and create an interference
pattern. The pattern would not be visible due to
f) Random phase difference between the light waves from the two sources.
g) Very high speed of light waves.
h) Diffraction of light through air molecules surrounding the bulbs.
i) Very short wavelengths of the light waves.
j) Inability of the human eyes to resolve two sources close together.
5. The colours in anti-reflective coatings on eyeglasses, solar cells, and the colours
seen as sunlight shines on a soap bubble, can be explained by
e) Light interfering as it reflects within a thin film.
f) Light diffracting within a thin film.
g) Light dispersing across a thick film.
h) Light polarizing inside a thin film.
6. Two identical waves which always interfere destructively must be out of phase
by
e) 90°
f) 180°
g) 270°
h) 360°
7. Calculate the speed of light in diamond (n = 2.42)
e) 1.24 x 𝟏𝟎𝟖 m/s
f) 7.26 x 108 m/s
g) 1.24 x 107 m/s
h) 7.26 x 107 m/s
8. Monochromatic light from a point source projected on an opaque screen with
two parallel slits spaced 2.5 x 10−5 meters apart has a first order bright fringe
that is 1.7° from the center. What is the wavelength?
f) 530 nm
g) 610 nm
h) 640 nm
i) 690 nm
j) 740 nm
9. The spectrum of light produced by a prism when white light travels through it is
caused by:
a) Making the ultraviolet and infrared wavelengths visible.
b) The bending of each wavelength of visible light through a slightly different
angle.
c) The diffraction of light by an obstacle.
d) A total internal reflection within the prism.
10. Of the five figures below, choose the one which most accurately illustrates single slit
diffraction from a monochromatic source.
Answer : b
Problems
1. Sodium vapour light with an average wavelength of 589 nm falls on a single slit, 7.5 x
10−6 m wide. Calculate
c) At what angle is the second minimum?
d) What is the highest order minimum produced.
2. A two point interference pattern in a water tank is formed by waves moving at 4.0
cm/s. A point on the third nodal line is located 22.0 from one source and 15.5 cm
from the other source. Find the wavelength and the frequency of waves. {wave
nature of light practice test.