Arbroath High School
Science
Department
Higher Physics
Interference,
Diffraction, Refraction
and Spectra.
Unit 2
Test 3
1. This pattern of maxima is produced by waves from two coherent sources,
S1 and S2.
S1
Central
maximum
S2
P
Q
R
The second maximum occurs at Q, where S1Q = 18 cm and S2Q = 14 cm.
The path difference for the 3rd minimum is
A
30 cm
B
37 cm
C
40 cm
D
47 cm
E
50 cm
1
2. The refractive index of perspex varies, depending on the colour of the light passing
through it.
Which of the following statements is/are true?
I
Blue light incident on a perspex block
gives it a higher refractive index than
would red light.
II
Blue light incident on a perspex block
gives it a lower refractive index than
would red light.
III Blue light travels more slowly through
a perspex block than red light.
A
I only
B
II only
C
III only
D
I and III only
E
II and III only
1
3.
Two speakers attached to a computer are placed on either side of it in a large room.
A pure 1 kHz test tone is fed to both speakers.
A pupil walks slowly across the floor in front of the speakers as shown.
Speaker 1
Speaker 2
P
Q
351 m
300 m
R
(a)
(b)
(i)
State what the pupil hears as he walks across the room.
1
(ii)
Explain carefully how the pattern of sound he hears is produced.
2
The pupil stops at R, where he is 351 m from speaker P and 300 m from speaker Q.
(i)
Assuming that the speed of sound in the room is 340 m s -1, calculate the
wavelength of the tone.
1
(ii)
What does the pupil hear at point R? Justify your answer with a
calculation.
3
(c)
What would happen to the sound pattern if a tone of a much higher frequency
were played?
1
4.
A violet light ray of frequency 746  1014 Hz is directed at an acrylic prism as shown.
Violet light ray
X
16°
n
θ
n
The refractive index of the acrylic is 153 for the violet light.
(a)
(b)
(i)
Calculate the value of the angle marked “θ”.
2
(ii)
Calculate the wavelength of the light inside the prism.
3
The violet light ray is replaced by a red ray. This ray is directed at the prism
at the same angle θ as in (a).
Will the angle marked “X” be bigger than, the same size as or smaller than it
`was for the violet light? You must justify your answer.
1
5.
The energy levels in an atom are shown below.
E3
-1·360 x 10-19 J
E2
-1·415 x 10-19 J
E1
-5·424 x 10-19 J
E0
-21·76 x 10-19 J
(a) State what is meant by:
(i)
The ionisation level.
1
(ii)
The ground state.
1
(b) How many lines will be observed in the line spectrum of this atom?
1
(c) Which transition will give the emitted radiation of the :
6.
(i)
Highest frequency.
2
(ii)
Longest wavelength.
2
This diagram represents some of the possible energy levels for the
Hydrogen atom.
E
-136  10-19J
3
E
-242  10-19J
2
E
-545  10-19J
1
E
-218  10-19J
0
(a)
(b)
How many spectral lines would these four energy levels produce?
1
Which transition for these levels would give the longest wavelength of
emitted radiation?
Explain your answer.
2
7.
Light of wavelength 500 nm is passed through a grating of 400 lines per mm.
A pattern of bright fringes is produced.
The angle between the zero and second order maxima is
8.
A
040 °
B
115 °
C
236 °
D
664 °
E
785°
1
The effect that a transparent block has on a laser beam is being studied.
This diagram shows the apparatus in use.
P
light meter
C
θ
Q
laser
The light meter is used to measure the irradiance of ray P as angle θ is varied.
(a)
(b)
Explain why a laser is used rather than a ‘white’ light ray box fitted with a
single slit.
2
What is meant by the “irradiance” of an electromagnetic radiation?
1