JEE Mains · Physics · STD 11 - 14. waves and sound
A driver in a car, approaching a vertical wall notices that the frequency of his car horn, has changed from \(440\, Hz\) to \(480 \,Hz ,\) when it gets reflected from the wall. If the speed of sound in air is \(345 \,m / s ,\) then the speed of the car is \(.......km/hr\)
- A \(36\)
- B \(24\)
- C \(18\)
- D \(54\)
Answer & Solution
Correct Answer
(D) \(54\)
Step-by-step Solution
Detailed explanation
\(f _{1}=\) frequency heard by wall \(= f _{ s }=\left(\frac{ v _{ s }}{ v _{ s }- v _{ c }}\right)\) \(f _{2}=\) frequency heard by driver after reflection from wall \(f_{2}=\left(\frac{v_{s}+v_{c}}{v_{s}}\right) f_{1}=\left(\frac{v_{s}+v_{c}}{v_{s}-v_{c}}\right) f_{0}\)…
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