What happens when the source speed exceeds the wave speed in the Doppler effect?

When the source speed exceeds the wave speed in the Doppler effect, it results in a shock wave or sonic boom.

In the Doppler effect, the frequency or wavelength of a wave changes for an observer moving relative to the source of the wave. This is a common phenomenon that can be observed in various types of waves, including sound, light, and radio waves. However, when the speed of the source exceeds the speed of the wave, the situation changes dramatically.

In the case of sound waves, if the source is moving faster than the speed of sound, it is said to be moving at supersonic speed. When this happens, the sound waves from the source can't keep up with the source itself. Instead of spreading out in a spherical pattern as they would normally, the waves are compressed into a cone-shaped pattern behind the source. This is known as a shock wave or sonic boom.

The sonic boom is not a one-time event that occurs when the source first exceeds the speed of sound. Rather, it is a continuous effect that occurs for as long as the source continues to move at supersonic speed. This is why a supersonic aircraft can be heard to create a sonic boom throughout its flight, not just when it first breaks the sound barrier.

The same principle applies to other types of waves as well. For example, in water, if a boat moves faster than the speed of the waves it creates, it will produce a wake of waves in a V-shaped pattern behind it. This is essentially the same phenomenon as a sonic boom, but with water waves instead of sound waves.

In summary, when the source speed exceeds the wave speed in the Doppler effect, it results in a shock wave or sonic boom. This is a dramatic demonstration of the Doppler effect, and it shows how the relative motion of the source and observer can have a significant impact on the observed frequency or wavelength of a wave.