A train standing at the outer signal of a railway station
blows a whistle of frequency \( 400 \m.... VIDEO
A train standing at the outer signal of a railway station
\( \mathrm{P} \)
blows a whistle of frequency \( 400 \mathrm{~Hz} \) in still air. The train begins to move with a speed of \( 30 \mathrm{~m} \mathrm{~s}^{-1} \) towards the platform. The frequency of the sound heard by an observer standing on the platform is (Speed of sound in air \( =330 \mathrm{~m} \mathrm{~s}^{-1} \) )
(1) \( 420 \mathrm{~Hz} \)
(2) \( 430 \mathrm{~Hz} \)
(3) \( 440 \mathrm{~Hz} \)
(4) \( 450 \mathrm{~Hz} \)
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