Q15.A source of sound A emitting waves of frequency 1800 Hz is falling towards ground with a terminal speed v. The observer B on the ground directly beneath the source receives waves of frequency 2150 Hz. The source A receives waves, reflected from ground of frequency nearly: (Speed of sound = 343 m/s ) (1) 2150 Hz (2) 2500 Hz (3) 1800 Hz (4) 2400 Hz
What This Question Tests
This multi-step problem applies the Doppler effect twice: first for the sound received by the observer from the falling source, and then for the reflected sound received by the falling source itself.
Concepts Tested
Formulas Used
f' = f₀ * (v ± v_o) / (v ∓ v_s)
f_reflected = f_ground * (v + v_s) / (v - v_s)
📚 NCERT Sections This Tests
14.6 — Reflection Of Waves
Physics Class 12 · Chapter 14
14.6 Reflection of waves some cork pieces on the disturbed surface, it is seen that
11.8 — Light Of Frequency 7.21 × 1014 Hz Is Incident On A Metal Surface.
Physics Class 12 · Chapter 11
11.8 Light of frequency 7.21 × 1014 Hz is incident on a metal surface. Electrons with a maximum speed of 6.0 × 105 m/s are ejected from the surface. What is the threshold frequency for photoemission of electrons?
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?
📋 Question Details
- Chapter
- Waves & Sound
- Topic
- Doppler effect
- Year
- 2014
- Shift
- 12 Apr Online
- Q Number
- Q15
- Type
- Multi concept
- NCERT Ref
- Class 11 Physics Ch 15: Waves
More from this Chapter
Q38.Tube A has both ends open while tube B has one end closed, otherwise they are identical. The ratio of fundamental frequency of tube A and B is (1) 1 : 2 (2) 1 : 4 (3) 2 : 1 (4) 4 : 1
Q39.A tuning fork arrangement (pair) produces 4 beats / sec with one fork of frequency 288cps. A little wax is placed on the unknown fork and it then produces 2 beats /sec. The frequency of the unknown fork is (1) 286 cps (2) 292 cps (3) 294 cps (4) 288 cps
Q40.A wave y = a sin(ωt −kx) on a string meets with another wave producing a node at x = 0. Then the equation of the unknown wave is (1) y = a sin(ωt + kx) (2) y = −a sin(ωt + kx) (3) y = a sin(ωt −kx) (4) y = −a sin(ωt −kx)
Q41.When temperature increases, the frequency of a tuning fork (1) increases (2) decreases (3) remains same (4) increases or decreases depending on the material