Question

A submarine is carefully navigating its way to the seafloor. It sends out “pings”—a radar wave—as it descends to keep track of its location in relation to the ground. The wavelength of the radar as it leaves the ship is 3 cm. Which of the following could be the wavelength as the wave returns? show work
A. 2 cm
B. 3 cm
C. 4 cm
D. impossible to estimate

Answer 1

Answer:

D. impossible to estimate

Explanation:

According to the doppler effect, the frequency of the wave will increase.

let u be the speed of the submarine,

let the speed of sound in water be c,

let initial frequency of the sent out wave be f,

let frequency of received wave be f'

The distance occupied by the new wave will be (c - u), therefore, the new wavelenght will be (c - u)/f

Frequency = speed of sound ÷ wavelenght

therefore the new Freq f' will be

f' = cf/(c - u) which will be shorter than the initial wavelenght.

But we do not know the speed of the submarine, so we can't estimate.