Which refers to the change in wavelength that occurs when an object moves toward or away from a light source?

'The Doppler Effect' is the correct answer.

I believe the answer is The Doppler Effect 

There is no graph to look at on here, but i shall explain them to you. a line graph is just in its title it’s a graph with a line running through the dots to show an increase or decrease. a bar graph is used to show how much or how little something is so a comparison. a scatter plot is used to graph points to tell the data. and i don’t know what a histogram is.