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Date November 2021 Marks available 2 Reference code 21N.2.HL.TZ0.8
Level Higher level Paper Paper 2 Time zone 0 - no time zone
Command term Show that Question number 8 Adapted from N/A

Question

The graph shows the variation with diffraction angle of the intensity of light after it has passed through four parallel slits.

The number of slits is increased but their separation and width stay the same. All slits are illuminated.

State what is meant by the Doppler effect.

[2]
a.

A plate performs simple harmonic oscillations with a frequency of 39 Hz and an amplitude of 8.0 cm.

Show that the maximum speed of the oscillating plate is about 20 m s−1.

[2]
b.

Sound of frequency 2400 Hz is emitted from a stationary source towards the oscillating plate in (b). The speed of sound is 340 m s−1.

Determine the maximum frequency of the sound that is received back at the source after reflection at the plate.

 

[2]
c.

State what will happen to the angular position of the primary maxima.

[1]
d.i.

State what will happen to the width of the primary maxima.

[1]
d.ii.

State what will happen to the intensity of the secondary maxima.

[1]
d.iii.

Markscheme

the change in the observed frequency ✓

when there is relative motion between the source and the observer ✓

 

Do not award MP1 if they refer to wavelength.

a.

use of 2πfA ✓

maximum speed is 2π×39×0.080=19.6 «m s−1» ✓

 

Award [2] for a bald correct answer.

b.

frequency at plate 2400×340+19.6340«=2538Hz»

at source 2538×340340-19.6=26942700 «Hz» ✓

 

Award [2] marks for a bald correct answer.

Award [1] mark when the effect is only applied once.

c.

stays the same ✓

d.i.

decreases ✓

d.ii.

decreases ✓

d.iii.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.
[N/A]
d.i.
[N/A]
d.ii.
[N/A]
d.iii.

Syllabus sections

Additional higher level (AHL) » Topic 9: Wave phenomena » 9.1 – Simple harmonic motion
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Additional higher level (AHL) » Topic 9: Wave phenomena
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