A siren placed at a railway platform is emitting sound of frequency 5 kHz. A passenger sitting in a moving train A records a frequency of 5.5 kHz, while the train approaches the siren. During his return journey in a different train B he records a frequency of 6.0 kHz while approaching the same siren. The ratio of the velocity of train B to that of train A is.
- 242/252
- 2
- 44687
- 44871
The Correct Option is B
Solution and Explanation
we get, $\hspace23mm 5.5=5 \bigg(\frac{v+v_A}{v}\bigg)\hspace20mm$...(i)
and $\hspace25mm 6.0=5 \bigg(\frac{v+v_B}{v}\bigg)\hspace25mm$...(ii)
Here, $\hspace10mm v = $ speed of sound
$\hspace20mm v_A = $ speed of train A
$\hspace20mm v_B = $ speed of train B
Solving Eqs. (i) and (ii), we get $\frac{v_B}{v_A}=2$
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Concepts Used:
Waves
Waves are a disturbance through which the energy travels from one point to another. Most acquainted are surface waves that tour on the water, but sound, mild, and the movement of subatomic particles all exhibit wavelike properties. inside the most effective waves, the disturbance oscillates periodically (see periodic movement) with a set frequency and wavelength.
Types of Waves:
Transverse Waves -
Waves in which the medium moves at right angles to the direction of the wave.
Examples of transverse waves:
- Water waves (ripples of gravity waves, not sound through water)
- Light waves
- S-wave earthquake waves
- Stringed instruments
- Torsion wave
The high point of a transverse wave is a crest. The low part is a trough.
Longitudinal Wave -
A longitudinal wave has the movement of the particles in the medium in the same dimension as the direction of movement of the wave.
Examples of longitudinal waves:
- Sound waves
- P-type earthquake waves
- Compression wave