Question

The diameter of a telescope’s mirror determines how much light it can gather. The amount of energy collected over the area of the mirror from the light of a particular star can be measured with sensitive instruments. How does the inverse square law then tell you the total energy given off by that star? At the Earth’s orbit the light of the Sun is distributed evenly over a sphere with a radius equal to that of the Earth’s orbit (about 1011 m.) The telescope has a 1-meter radius (2-meter diameter). What fraction of the Sun’s light can the telescope capture?

Answer 1