Which statement best describes the effect of the sun's angle on daily insolation?

• A. Higher angle yields less insolation
• B. Insolation is independent of latitude
• C. Latitude has no effect on day length
• D. Higher angle yields more intense insolation

Answer: (D)

Sun angle controls how much solar energy reaches a location because when the sun is high, rays hit the surface more directly, concentrating energy on a smaller area. The energy per unit area increases as the sun’s altitude rises because the path through the atmosphere is shorter, so less energy is lost to scattering and absorption. This makes daily insolation more intense. When the sun is low, rays are oblique and travel through more atmosphere, spreading energy over a larger area and reducing what reaches the surface. Because the sun’s height varies with latitude and the season, insolation changes across the globe. Statements claiming insolation is independent of latitude or that latitude has no effect on day length ignore this geometry. So, a higher sun angle yields more intense daily insolation.