Q12.A train moves towards a stationary observer with speed 34 m/s. The train sounds a whistle and its frequency registered by the observer is f1. If the speed of the train is reduced to 17 m/s, the frequency registered is f2. If speed of sound is 340 m/s, then the ratio f1/f2 is: (1) 21/20 (2) 20/19 (3) 19/18 (4) 18/17
What This Question Tests
This problem applies the Doppler effect formula for sound waves twice, with different source velocities, to find the ratio of observed frequencies.
Concepts Tested
Formulas Used
f' = f * (v_sound ± v_observer) / (v_sound ± v_source)
📚 NCERT Sections This Tests
12.6 — (A) Using The Bohr’S Model Calculate The Speed Of The Electron In A
Physics Class 12 · Chapter 12
12.6 (a) Using the Bohr’s model calculate the speed of the electron in a hydrogen atom in the n = 1, 2, and 3 levels. (b) Calculate the orbital period in each of these levels.
10.3 — (A) The Refractive Index Of Glass Is 1.5. What Is The Speed Of Light In
Physics Class 12 · Chapter 10
10.3 (a) The refractive index of glass is 1.5. What is the speed of light in glass? (Speed of light in vacuum is 3.0 × 108 m s–1) (b) Is the speed of light in glass independent of the colour of light? If not, which of the two colours red and violet travels slower in a glass prism?
12.6 — (A) 2.18 × 106 M/S; 1.09 × 106 M/S; 7.27 × 105 M/S
Physics Class 12 · Chapter 12
12.6 (a) 2.18 × 106 m/s; 1.09 × 106 m/s; 7.27 × 105 m/s (b) 1.52 × 10–16 s; 1.22 × 10–15 s; 4.11 × 10–15 s.
📋 Question Details
- Chapter
- Waves & Sound
- Topic
- Doppler effect in sound
- Year
- 2019
- Shift
- 10 Jan Shift 1
- Q Number
- Q12
- Type
- MCQ
- NCERT Ref
- Class 11 Physics Ch 15: Waves
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