B) A train on a straight track sounds a 400 Hz horn when passing a parked car on the road. The train is moving at 20 m/s and the temperature is 10celsius degree . Find the apparent frequency of the horn for a person sitting inside the car when the train is approaching and when the train is moving away.

Reflection of sound waves

A boat is floating at rest in dense fog near a large cliff. The captain sounds a horn at water level and the sound travels through the salt water (1470 m/s) and the air (340m/s) simultaneously. The echo in the water (due to the cliff) takes 0.40s to return. How much additional time will it take for the echo in the air to return?