Review 4 (4.3, 4.4, 4.5)
[111
marks]
This question is in two parts. Part 1 is about wave motion. Part 2 is about the
melting of the Pobeda ice island.
Part 1 Wave motion
1a. State what is meant by the terms ray and wavefront and state the
relationship between them.
[3 marks]
1b. The diagram shows three wavefronts, A, B and C, of a wave at a
[4 marks]
particular instant in time incident on a boundary between media X and Y.
Wavefront B is also shown in medium Y.
(i) Draw a line to show wavefront C in medium Y.
(ii) The refractive index of X is nX and the refractive index of Y is nY. By making
n
appropriate measurements, calculate nX .
Y
1c. Describe the difference between transverse waves and longitudinal
waves.
[2 marks]
1d. The graph below shows the variation of the velocity v with time t for one [3 marks]
oscillating particle of a medium.
(i) Calculate the frequency of oscillation of the particle.
(ii) Identify on the graph, with the letter M, a time at which the displacement of
the particle is a maximum.
2. A beam of unpolarized light is incident on the surface of a liquid and is
partially reflected and partially refracted as shown below.
[1 mark]
The reflected light is completely horizontally polarized. Which of the following is
the refractive index of the liquid?
A. tan 40°
B. tan 50°
sin 40∘
sin 50∘
sin 40∘
D.
cos 50∘
C.
3. Unpolarized light is incident on a polarizer. The light transmitted by the [1 mark]
first polarizer is then incident on a second polarizer. The polarizing axis of
the second polarizer is at 60º to that of the first polarizer.
The intensity emerging from the second polarizer is If.
Which of the following correctly gives the intensity incident on the first polarizer?
If
A. 8
If
B. 4
C. 4 If
D. 8If
This question is about polarization.
4a. State what is meant by polarized light.
[1 mark]
4b. Light of intensity I0 is incident on a polarizer. The transmission axis of
[4 marks]
the polarizer is vertical. The polarizer is rotated by an angle θ about the
direction of the incident light. The intensity of the transmitted light is measured for
various angles θ.
On the axes below, sketch graphs to show the variation of the transmitted
intensity I with θ when the incident light is
(i) horizontally polarized.
(ii) unpolarized.
5. Polarized light of intensity I0 is incident on a polarizing filter. The angle
[1 mark]
between the plane of polarization of the incident light and the
transmission plane of the polarizer is θ. Which graph shows how the intensity I of
the light transmitted through the polarizer varies with θ?
This question is about polarization.
6a. State what is meant by polarized light.
[1 mark]
11. Monochromatic light travelling upwards in glass is incident on a boundary [1 mark]
with air. The path of the refracted light is shown.
A layer of liquid is then placed on the glass without changing the angle of
incidence on the glass. The refractive index of the glass is greater than the
refractive index of the liquid and the refractive index of the liquid is greater than
that of air.
What is the path of the refracted light when the liquid is placed on the glass?
13b. The speed of sound c for longitudinal waves in air is given by
[3 marks]
c = √ Kρ
where ρ is the density of the air and K is a constant.
A student measures f to be 120 Hz when the length of the pipe is 1.4 m. The
density of the air in the pipe is 1.3 kg m–3. Determine, in kg m –1 s–2, the value of K
for air.
A beam of coherent monochromatic light from a distant galaxy is used in an optics
experiment on Earth.
The beam is incident normally on a double slit. The distance between the slits is
0.300 mm. A screen is at a distance D from the slits. The diffraction angle θ is
labelled.
14a. A series of dark and bright fringes appears on the screen. Explain how a [3 marks]
dark fringe is formed.
14b. The wavelength of the beam as observed on Earth is 633.0 nm. The
separation between a dark and a bright fringe on the screen is 4.50
mm. Calculate D.
[2 marks]