Q25.Two cars X and Y are approaching each other with velocities 36 km h−1 and 72 km h−1 respectively. The frequency of a whistle sound as emitted by a passenger in car X, heard by the passenger in car Y is 1320 Hz. If the velocity of sound in air is 340 ms−1, the actual frequency of the whistle sound produced is ________ Hz.
What This Question Tests
This question tests the application of the Doppler effect formula for sound waves when both the source and observer are moving towards each other.
Concepts Tested
Formulas Used
f' = f * (v_sound ± v_observer) / (v_sound ± v_source)
📚 NCERT Sections This Tests
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?
2.5 — A Parallel Plate Capacitor With Air Between The Plates Has A
Physics Class 11 · Chapter 2
2.5 A parallel plate capacitor with air between the plates has a capacitance of 8 pF (1pF = 10–12 F). What will be the capacitance if the distance between the plates is reduced by half, and the space between them is filled with a substance of dielectric constant 6?
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 in sound
- Year
- 2021
- Shift
- 27 Aug Shift 1
- Q Number
- Q25
- Type
- Numerical
- 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