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Chapter 29 of 30
Important Questions

Doppler effect — Important Questions

ICSE · Class 11 · Physics

40 important questions from Doppler effect for ICSE Class 11 Physics, with answers. Includes multiple choice questions.

40 questions30 flashcards10 formulas & key relations5 concepts

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40 Questions·
multiple choice

Important Questions from Doppler effect

1multiple choice
3 marks

A car moves towards a stationary wall at 18 m/s and blows a horn of frequency 450 Hz. Take speed of sound as 330 m/s. What frequency does the wall receive first?

Show answer

476 Hz

First treat the wall as a stationary observer. Use n1 = n(v/(v-v_c)). Here n = 450 Hz, v = 330 m/s, v_c = 18 m/s. So n1 = 450 × 330/312 = 450 × 1.057692... = 476.0 Hz.

2multiple choice
3 marks

A source and an observer move in the same direction of sound with speeds 14 m/s and 6 m/s respectively. The true frequency is 700 Hz and sound speed is 340 m/s. What is the apparent frequency?

Show answer

717 Hz

Use n' = n((v-v_o)/(v-v_s)). Here n = 700 Hz, v = 340 m/s, v_o = 6 m/s, v_s = 14 m/s. So n' = 700 × 334/326 = 700 × 1.024540... ≈ 717.2 Hz. Hence 717 Hz.

3multiple choice
3 marks

A source of 300 Hz moves away from an observer at 10 m/s, while the observer moves towards the source at 20 m/s. Take sound speed as 330 m/s. What is the apparent frequency?

Show answer

309 Hz

Because the source recedes and the observer approaches, use n' = n((v+v_o)/(v+v_s)). Here n = 300 Hz, v = 330 m/s, v_o = 20 m/s, v_s = 10 m/s. So n' = 300 × 350/340 = 308.82 Hz, which rounds to 309 Hz.

4multiple choice
3 marks

A wind of 12 m/s blows in the direction of sound. A stationary source emits 540 Hz and a stationary observer receives it. What is the apparent frequency?

Show answer

540 Hz

If both source and observer are stationary, n' = n regardless of wind. Here n = 540 Hz, so the apparent frequency remains 540 Hz.

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Frequently Asked Questions

What are the important topics in Doppler effect for ICSE Class 11 Physics?
Key topics in Doppler effect include Doppler Effect in Sound, Reflected Sound, Non-Collinear Motion, Doppler Effect in Light. Study these first, then practise questions on each for Class 11 exams.
How many important questions are there in Doppler effect?
Super Tutor has 40 practice questions for Doppler effect, including multiple choice questions. A sample with answers is on this page.

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