question_answer

In summer, the sound of a siren is heard louder in the night than in the day to a person on the earth. Why?

Answer:

                During the day, the temperature of the earth is maximum near the ground and it progressively decreases upwards. The velocity of sound is maximum near the ground and decreases upwards\[(\upsilon \propto \sqrt{T}).\] The vertical plane wave fronts produced by the siren continuously bend upwards, so the sound waves curl upwards during the day. The temperature conditions are reversed at night. The sound waves curl downwards, making the sound of siren louder on the earth.