What is the intensity of sunlight per square meter reaching Venus compared with this intensity at Earth's orbital distance? (Venus's orbit has a semimajor axis of about 0.7 au.)
A) about the same, since this intensity remains constant, following a law of nature
B) about 1.4
C) about 1.9
D) about 0.5

Question

Quizplus · Accepted Answer

The intensity of sunlight reaching a planet decreases with the square of the distance from the Sun. Since Venus is about 0.7 astronomical units (au) from the Sun, compared to Earth's 1 au, the intensity of sunlight per square meter on Venus is about $(1/0.7)^2 \approx 2$, or specifically about 1.9 times the intensity at Earth.

What Is the Intensity of Sunlight Per Square Meter Reaching