Which of the following refers to the change in wavelength that occurs when an object moves toward or away from a source?
a) doppler effect
b) chromatic aberration
c) spectroscopy
d) wave theory of light

A) Doppler effect

Explanation:

As we know that when Sound source travel with respect to observer then due to relative motion of source and observer the frequency of sound emitted by the source is observed slightly different by the observer.

This change in the frequency of the sound observed by the observer is known as Doppler's Effect

So here we know by the formula of doppler's effect the frequency is given as

so here since the frequency observed is different from real frequency so the wavelength observed by the observer is changed

so correct answer will be

A) Doppler effect

i would think it's food chain