• An objects?luminosity?depends on two factors:
  • Its surface temperature
  • Its surface area

   

• The relationship between these is known as the?Stefan-Boltzmann Law, which states:

The total energy emitted by a black body per unit area per second is proportional to the fourth power of the absolute temperature of the body

• So,?L?∝?AT4
• The Stefan-Boltzmann Law equation is:

L = σAT4

• Where:
  • L?=?luminosity?of the star (W)
  • A?= surface area of the star
  • σ = the?Stefan-Boltzmann constant
  • T?= surface temperature of the star (K)

• The surface area of a star (or other spherical object) can be calculated using:

A =?4πr2

• Where:
  • r =?radius of the star

Step 1: Write down the equation

L = σAT4

Step 2:?Convert temperature from ?C to K

• • 40 + 273 = 313 K

Step 3: Substitute in the values

• • L?= (5.67 × 10–8) × 16 × 3134?= 29387 W = 8 707

Step 4: Write answer to correct significant figures and include units

Luminosity (power emitted) of the camel = 8 700 W (2 sig figs)