When we look at a star
that is 50.000 light
years away we are seeing it as

Please help

I'm not really sure what specific answer they're looking for, but if it's an open-ended question, then let's think about it this way...

A light year, is the distance it takes for light to travel in a year. If an object is 50,000 light years away, then by the time the light travels to us, 50,000 years has passed. We are looking at a 50,000 year old image of that object. (ignoring gravity and spatial expansion fun stuffs)

show the wavelengths of a wave. show the crests of a wave.

it is called kinetic energy