- #1

Karol

- 1,380

- 22

## Homework Statement

I read that when a body approaches a stationary one which emits radar waves, the wavelength λ

_{2}of the returned waves is longer than λ

_{1}, the wavelength of the emitted ones, but I get the opposite. I suppose this is true for sound waves also.

See picture.

## The Attempt at a Solution

Velocity of sound in the air: u

Velocity of approaching object: v

The frequency at which the waves from the stationary source hit the moving object:

[tex]f_1=\frac{u+v}{\lambda_1}[/tex]

The wavelength of the reflected wave:

[tex]\lamda_2=\frac{u-v}{f_1}=\frac{(u-v)\lambda_1}{u+v}[/tex]

Now:

[tex]\frac{u-v}{u+v}<1\rightarrow\lambda_1>\lambda_2[/tex]