When an ambulance with a blaring siren moves towards an observer, the pitch of the siren appears to be higher. This is due to: MCQ with Answer and Explanation
When an ambulance with a blaring siren moves towards an observer, the pitch of the siren appears to be higher. This is due to:
A. Acoustic resonance
B. Interference of sound waves
C. Reverberation
D. The Doppler Effect
Answer: Option D
Solution (By JKSSB Mock Tests)
The Doppler Effect is the apparent change in the frequency (and thus pitch) of a wave due to the relative motion between the source and the observer. As the ambulance approaches, sound waves get compressed, increasing the perceived frequency (higher pitch). As it moves away, waves stretch, lowering the frequency.
Explanation:
Laser (Light Amplification by Stimulated Emission of Radiation) requires that more atoms exist in a high-energy excited state than in a lower energy state. This unnatural, non-equilibrium condition is called 'population inversion'. Without it, absorption would dominate over stimulated emission, and the beam would not be amplified.
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