DP Physics (last assessment 2024)

Question 20N.2.HL.TZ0.4c

Date	November 2020	Marks available	[Maximum mark: 2]	Reference code	20N.2.HL.TZ0.4c
Level	HL	Paper	2	Time zone	TZ0
Command term	Estimate	Question number	c	Adapted from	N/A

[Maximum mark: 2]

20N.2.HL.TZ0.4c

Two loudspeakers, A and B, are driven in phase and with the same amplitude at a frequency of $850 Hz$ . Point P is located $22.5 m$ from A and $24.3 m$ from B. The speed of sound is $340 m s^{- 1}$ .

(c)

When both loudspeakers are operating, the intensity of sound recorded at Q is $I_{0}$ . Loudspeaker B is now disconnected. Loudspeaker A continues to emit sound with unchanged amplitude and frequency. The intensity of sound recorded at Q changes to $I_{A}$ .

Estimate $\frac{I_{A}}{I_{0}}$ .

[2]

Markscheme

the amplitude of sound at Q is halved ✓
«intensity is proportional to amplitude squared hence» $\frac{I_{A}}{I_{0}} = \frac{1}{4}$ ✓

Examiners report

Most candidates earned 2 marks or nothing. A common answer was that intensity was 1/2 the original.

Syllabus sections

Core

Core » Topic 4: Waves » 4.3 – Wave characteristics

Core » Topic 4: Waves

Question 20N.2.HL.TZ0.4c

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