1.6 Using radiation to investigate stars

Question 1

What is a black body?

Answer 1

A body that absorbs all incoming radiation that falls on it.

Question 2

What is an absorption spectrum?

Answer 2

As a continuous spectrum of light (white) passes through a medium (e.g. a gas cloud) some of the electron of certain atoms will absorb particular wavelengths of incoming photons. This absorption will result in lines appearing on a spectrum where these wavelengths have been absorbed

Question 3

What is Wien’s law?

Answer 3

It states that the wavelength of peak emission from a black body is inversely proportional to the absolute (kelvin) temperature of the body
λ max= W/T
Peak wavelength = Wein’s constant/ Temperature

Wein’s Constant = 2.90 x 10^-3 mK

Question 4

What is Stefan’s law?

Answer 4

The total electromagnetic radiation energy emitted per unit time by a black body is given by
P = AσT⁴
Where A is the surface area (4πr²), σ is Stefan’s Constant (5.67 x 10^-8)

Question 5

What is the inverse square law?

Answer 5

I = P/4πR²
The intensity of radiation from a star per m² is inversely proportional to the distance from the star squared