Solar energy?

How does the angle the light makes (Ex. the angle of the sun’s rays) with the surface affect solar energy?
here the experiment
The inside of a shoe box was insulated using Styrofoam and a thermometer was placed through a hole inside the box. Two absorbing surfaces were made from aluminum foil. The upper surface of one sheet was painted black and the other left shiny. The following tests were then carried out.

A sheet of shiny aluminum was placed in the bottom of the box. The top of the box was covered with glass and the temperature of the air inside the box was recorded. The lamp was then turned on and the temperature was recorded after 3 minute.

The procedure was repeated, this time using the blackened aluminum as the absorbing surface. Three set of data were collected. One test was done with the glass cover, one without the glass cover and the third with a glass cover but at an angle of 45ยบ.