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Chapter 29 of 30
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Doppler effect

ICSE · Class 11 · Physics

Flashcards for Doppler effect — ICSE Class 11 Physics. Quick Q&A cards covering key concepts, definitions, and formulas.

40 questions30 flashcards5 concepts

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30 Flashcards
Card 1Definition

State the Doppler effect for sound.

Answer

The apparent change in the frequency of the source due to a relative motion between the source and the observer is known as Doppler effect.

Card 2Concept of frequency change

Why does sound pitch change when a source and observer move relative to each other?

Answer

If the distance between source and observer decreases, wavefronts reach the observer more often, so frequency appears increased. If the distance increases, wavefronts reach less often, so frequency ap

Card 3Basic formula

State the wavelength of sound from a stationary source.

Answer

Formula: λ = v/n Meaning: λ = wavelength, v = velocity of sound, n = true frequency. This is the wavelength when the source is stationary.

Card 4Numerical on wavelength

A source emits sound of frequency 500 Hz in air where v = 331 m/s. Find wavelength when the source is stationary.

Answer

Given: n = 500 Hz, v = 331 m/s Formula: λ = v/n Step 1: λ = 331/500 m Step 2: λ = 0.662 m Answer: 0.662 m

Card 5Moving source toward observer

State the apparent frequency when a source moves towards a stationary observer.

Answer

Formula: n' = n(v/(v-v_s)) Meaning: n = true frequency, v = sound velocity, v_s = source velocity. This gives a frequency greater than the true frequency.

Card 6Numerical on moving source

A source of frequency 400 Hz moves towards a stationary observer with speed 20 m/s. Take v = 331 m/s. Find the apparent frequency.

Answer

Given: n = 400 Hz, v = 331 m/s, v_s = 20 m/s Formula: n' = n(v/(v-v_s)) Step 1: v - v_s = 331 - 20 = 311 m/s Step 2: n' = 400 × (331/311) Step 3: n' ≈ 425.7 Hz Answer: about 426 Hz

Card 7Moving source away from observer

State the apparent frequency when a source recedes from a stationary observer.

Answer

Formula: n' = n(v/(v+v_s)) Meaning: the apparent frequency is less than the true frequency when the source moves away.

Card 8Numerical on receding source

A source of frequency 600 Hz moves away from a stationary observer with speed 31 m/s. Take v = 331 m/s. Find the apparent frequency.

Answer

Given: n = 600 Hz, v = 331 m/s, v_s = 31 m/s Formula: n' = n(v/(v+v_s)) Step 1: v + v_s = 331 + 31 = 362 m/s Step 2: n' = 600 × (331/362) Step 3: n' ≈ 548.6 Hz Answer: about 549 Hz

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Frequently Asked Questions

What are the important topics in Doppler effect for ICSE Class 11 Physics?
Doppler effect covers several key topics that are frequently asked in ICSE Class 11 board exams. Focus on the core concepts listed on this page and practise related questions to build confidence.
How to score full marks in Doppler effect — ICSE Class 11 Physics?
Understand the core concepts first, then work through the 40 practice questions available for this chapter. Revise formulas and definitions regularly, and use flashcards for quick recall before the exam.
How many flashcards are available for Doppler effect?
There are 30 flashcards for Doppler effect covering key definitions, formulas, and concepts. Use them daily for 10–15 minutes for best results.

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