Angle of incidence of sun's rays
Also called: Angle of inclination of sun's rays · Topic: Solar Radiation, Heat Balance and Temperature · NCERT: Class 7, Ch 3 "Climates of India"; Class 9, Ch 3 "Atmosphere and Climate"; Class 11, Ch 8 "Solar Radiation, Heat Balance and Temperature"
Meaning
The angle of incidence is the angle at which the Sun's rays strike the ground. It depends mainly on latitude (distance north or south of the equator). When rays fall vertically, their energy is packed into a small area, so they heat it strongly. When rays fall at a slant, the same energy spreads over a larger area. Slanting rays also pass through more air, so more energy is absorbed and scattered (bounced in all directions) on the way. So they heat the ground less.
Example
In December, the noon Sun is high in the sky over Kanyakumari (about 8°N), so the place stays warm. Over Srinagar (about 34°N), the Sun is low and its rays are slanting, so winter there is cold.
Don't confuse with
- Aspect: aspect is about which direction a slope faces. It changes how much sunlight that particular slope gets. The angle of incidence is set mainly by latitude.