The above temperature is Earth's as seen from space, not ground temperature but an average over all emitting bodies of Earth from surface to high altitude. This approximation reduces the temperature by a factor of 0.7 1/4, giving 255 K (−18 ☌ −1 ☏). The effect of albedo on temperature can be approximated by assuming that the energy absorbed is multiplied by 0.7, but that the planet still radiates as a black body (the latter by definition of effective temperature, which is what we are calculating).

No passive optical system can increase the specific. There are other intensity-related units in use, too. Thus the conservation of specific intensity (Equation 2.7) implies that total intensity defined as. If you double the amplitude of a wave you give it four times as much energy, this leads on to the relationship between amplitude and intensity of a wave. For example, infrared and visible energy from the Sun impinge on Earth at an intensity of 1300 W / m 2 just above the atmosphere. Intensity is a measure of the power transferred per unit area. The Earth has an albedo of 0.3, meaning that 30% of the solar radiation that hits the planet gets scattered back into space without absorption. The SI unit for intensity is watts per square meter ( W / m 2). This gives an effective temperature of 6 ☌ on the surface of the Earth, assuming that it perfectly absorbs all emission falling on it and has no atmosphere. It is a three-dimensional form of the wave equation. Where T ⊙ is the temperature of the Sun, R ⊙ the radius of the Sun, and a 0 is the distance between the Earth and the Sun. Example 1: Calculating intensity and power: How much energy is in a ray of Sunlight Begin with the equation that states the definition of intensity. The electromagnetic wave equation is a second-order partial differential equation that describes the propagation of electromagnetic waves through a medium or in a vacuum. It turns out that all phenomena (such as sound or light) which obey the wave-equation obey a very similar formula. Not to be confused with Stefan's equation or Stefan's formula.

Intensity light power equation