The frequency of light from a moving object changes due to the Doppler effect. This effect is a change in the observed frequency of a wave (like light) when the source of the wave and the observer are moving relative to each other.

Here's how it works:

* Moving Towards: When a light source is moving towards an observer, the light waves are compressed, causing the frequency to increase. This is known as blueshift, because the light shifts towards the blue end of the electromagnetic spectrum.

* Moving Away: When a light source is moving away from an observer, the light waves are stretched out, causing the frequency to decrease. This is known as redshift, because the light shifts towards the red end of the electromagnetic spectrum.

Key points about the Doppler effect for light:

* Speed: The faster the relative motion between the source and the observer, the greater the frequency shift.

* Direction: The direction of motion matters. Moving towards leads to blueshift, moving away leads to redshift.

* Not Just Light: The Doppler effect applies to all waves, including sound waves.

Applications of the Doppler effect for light:

* Astronomy: Redshift is used to measure the distance and speed of distant galaxies and stars.

* Radar: The Doppler effect is used in radar systems to determine the speed of objects, like cars or aircraft.

* Medical Imaging: Doppler ultrasound uses the Doppler effect to measure blood flow in the body.

Let me know if you'd like more details on any of these applications!