Stellar luminosity

Question 1

What is a black body?

Answer 1

An idealised object that absorbs all the electromagnetic radiation that shines onto it and when, in thermal equilibrium, emits a characteristic distribution of wavelengths at a specific temperature.

Question 2

What is Wien’s displacement law?

Answer 2

Maximum wavelength is inversely proportional to T

Question 3

What is Stefan’s law?

Answer 3

The total power radiated per unit surface area of a black body is directly proportional to the fourth power of the absolute temperature of the black body.

Question 4

What does Stefan’s law show?

Answer 4

The lumionsity of a star is directly proportional to:

• its radius squared
• surface area
• absolute temperature to the power of 4

Question 5

What is luminosity?

Answer 5

The total energy a star emits per second i.e. its power output.