I know a car sounds different approaching vs leaving but what is happening re sound waves and is there a similar effect with light waves?
In: 0
It helps to think of the wave as a series of baseballs being flung at you. Each peak being a ball. And these balls are magic balls that always travel at the same speed, regardless of the velocity of thing throwing them.
Now say you mounted a gun that shot these baseballs at a set interval on top of a car.
Let’s say it fires balls one per second, no matter the speed of the car. These balls travel at 100 meters per second, no matter what the speed of the car.
But the car is also traveling towards you at 10m/s. So each subsequent ball, while traveling the exact same speed, has to cover a shorter distance to reach you. If the first ball is fired at 1000 meters, it takes ten seconds to reach you. The next takes 9.9, the next 9.8….
So the frequency of balls hitting you increases, even though they are leaving the source at a constant interval.
Driving away, it’s the opposite. The balls have to cover increasing distances every time, so they hit you les and less frequently.
And yes, this applies to light. You may have heard the terms “red shift” and “blue shift” which correspond to the lowering and raising of electromagnetic wave frequency as objects move away or towards the observer. Red light is the lower frequency end of the visible light spectrum, and blue the higher. The terms can apply to frequencies outside the visible spectrum as well though.
Latest Answers