Question

Lidia plans an experimental investigation to see how the thickness of a lens affects the point where a beam of light is focused. She plans to shine light through a lens and measure the distance to a screen that is placed where the beam focuses.

What are the controls in Lidia’s investigation?

the material and thickness of the lens
the type of light and the material of the lens
the distance to the screen and the type of light
the thickness of the lens and the distance to the screen