Waves Review
1.
This question is about the Doppler effect.
The sound emitted by a car’s horn has frequency f, as measured by the driver. An observer moves
towards the stationary car at constant speed and measures the frequency of the sound to be f ′.
(a)
Explain, using a diagram, any difference between f ′ and f.
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(3)
(b)
The frequency f is 3.00 × 102 Hz. An observer moves towards the stationary car at a
constant speed of 15.0 m s–1. Calculate the observed frequency f ′ of the sound.
The speed of sound in air is 3.30 ×102 m s–1.
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(2)
(Total 5 marks)
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2.
This question is about optical resolution and accommodation.
A woman is walking along a straight path, which is at right angles to a telephone line, as shown in
the diagram below. Two birds are perched on the line, 0.40 m apart.
(diagram not to scale)
The diameter of the pupil of the woman’s eye is 2.5 mm and the average wavelength of visible
light is 550 nm.
(a)
Use the Rayleigh criterion to estimate the distance D at which the woman will just be able
to see two separate birds.
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(3)
(b)
The woman looks down at her watch and is able to focus on it clearly. Explain how her eyes
are able to focus on near objects as well as far objects.
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(2)
(Total 5 marks)
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3.
The fundamental (first harmonic) frequency for a particular organ pipe is 330 Hz. The pipe is
closed at one end but open at the other. What is the frequency of its second harmonic?
A.
110 Hz
B.
165 Hz
C.
660 Hz
D.
990 Hz
(Total 1 mark)
4.
Light is diffracted at a single slit. Which of the following graphs best represents how the intensity
I of the diffracted light varies with the diffraction angle θ?
A.
B.
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C.
D.
(Total 1 mark)
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5.
Plane-polarized light is incident normally on a polarizer which is able to rotate in the plane
perpendicular to the light as shown below.
In diagram 1, the intensity of the incident light is 8 W m–2 and the transmitted intensity of light is
2 W m–2. Diagram 2 shows the polarizer rotated 90° from the orientation in diagram 1. What is the
new transmitted intensity?
A.
0 W m–2
B.
2 W m–2
C.
6 W m–2
D.
8 W m–3
(Total 1 mark)
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6.
The images of two sources are just resolved. Which of the following is a correct statement of the
Rayleigh criterion for this situation?
A.
The central maximum of the diffraction pattern of one source must coincide with the
central maximum of the diffraction pattern of the other source.
B.
Light from the sources must pass through a circular aperture.
C.
Light from the sources must be coherent.
D.
The first minimum of the diffraction pattern of one source must coincide with the central
maximum of the diffraction pattern of the other source.
(Total 1 mark)
7.
An optically active substance is a substance that
A.
has a refractive index that depends on the plane of polarization of incident light.
B.
completely absorbs incident unpolarized light.
C.
rotates the plane of polarization of incident polarized light.
D.
polarizes unpolarized light.
(Total 1 mark)
8.
In a monochromatic liquid crystal display (LCD), such as those used in calculators, the purpose of
the liquid crystal is to
A.
change colour from white to black when a segment is to be displayed.
B.
lubricate the small gap between the plates to prevent overheating.
C.
rotate the plane of polarization of the light passing through it.
D.
act as a conducting pathway between the segment electrodes.
(Total 1 mark)
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