Question

A bat moving at 10 ms⁻¹ towards a wall sends a sound signal of 8000 Hz towards it. On reflection, it hears a sound of frequency f The value of f in Hz is close to (speed of sound = 320 ms⁻¹)

Options

• 8516

• 8258

• 8424

• 8000

Answer 1

8516

Explanation:

Sound frequency reflected by the bat

= `[("V" - (-"V"_0))/("V" - "V"_"s")] f = [("V" + "V"_0)/("V" - "V"_"s")] f = ("V" + 10)/("V" - 10) f`

= `((320 + 10)/(320 - 10)) xx 8000`

 = 856 Hz