Two cars are moving towards each other at the speed of 50 ~ms ⁻¹ . If one of the cars blows a horn at a frequency of 250 ~Hz , the wave length of the sound perceived by the driver of the other car is (Speed of sound in air =350 ~ms ⁻¹ )

Step-by-step solution

Here, both cars are moving towards each other, hence one car is like an observer and another car is like a source. v_s=50 ~m / s v₀=-50 ~m / s Frequency of horn blown by the source car, v=250 ~Hz According to Doppler's effect, frequency heared by another car v ' is given as v^ = v-v₀ v-v_s v= 350-(-50) 350-50 250 (v= speed of sound =350 ~m / s )= 400 250 300 v^ = 100 3 ~Hz Wavelength of heard sound, ^ = v v^ = 350 1000 / 3 = 1050 1000 =1.05 ~m =105 ~cm