Adog whistle uses a frequency higher than humans can normally hear. a pet owner wants to test his dog whistle. the owner has a drive a car and blow the whistle while he stands on the sidewalk. in which direction should the driver drive so that the pet owner can hear it and why? a) the driver should drive away from the pet owner to use the doppler effect. b) the driver should drive toward the pet owner to make the frequency lower. c) the driver should drive away from the pet owner to change the speed of sound. d) the driver should drive away from the pet owner to use make the frequency higher.

A) The driver should drive away from the pet owner to use the Doppler effect

Explanation:

The whistle claims to be making a frequency higher than the audible frequency to humans

We need to decrease its frequency to make it audible.

Doppler effect explains the influence of motion of the source on the observed frequency.

If the source is approaching the observed frequency will be higher than the real frequency.

For an approaching source

If the source is receding the observed frequency will be lower than the real frequency

For a receding source

From the above facts we understand that the helper should ride away from the pet owner to decrease the frequency and make the whistle audible.

a longitudinal wave moves energy that is to the direction of the wave’s movement. - true