Reflecting telescopes are popular because they are more durable than a refracting telescopes.
There is a difference between these two types of telescopes, reflecting telescopes worked by reflecting light, they are also known as reflector and refracting telescopes worked by refracting light and they are also known as reflactor.
Reflecting telescopes also provides a good focus.
Elastic potential energy is equal to the force times the distance of movement. Elastic potential energy = force x distance of displacement. Because the force is = spring constant x displacement, then the Elastic potential energy = spring constant x displacement squared.
The answer for this question is Control Variable because it doesn’t change throughout the experiment.
