Using radiation to investigate the stars

Question 1

What is the layer of gas that stars emit light from called?

Answer 1

The photosphere.

Question 2

What is a black body?

Answer 2

A body or surface which absorbs all the electromagnetic radiation that falls upon it (eg stars).

Question 3

What is the line emission spectrum?

Answer 3

Observed for a low pressure atomic gas
An atom absorbs energy which excites an electron to a higher level. The electron then falls back down to the lowest possible energy level and emits a photon of em radiation
Each electron gives out a particular wavelength photon which forms the line spectrum
Appears as a few lines of colour on a black background when viewed through a diffraction grating

Question 4

What is the continuous emission spectrum?

Answer 4

All wavelengths of light are present from red to violet.

Question 5

What is the line absorption spectrum?

Answer 5

When white light is passed through a cool atomic gas, dark lines are observed in the continuous spectrum. The atoms of the gas absorb certain wavelength photons. Appears as dark lines on a continous spectrum background when viewed through a diffraction grating.

Question 6

What is Wiens law?

Answer 6

λmax (m) = W (mK) / T (K)

Question 7

What is spectral intensity?

Answer 7

The amount of light energy striking each metre squared per second (Wm-2).

Question 8

What is the inverse square law of light?

Answer 8

The intensity of light observed from a source is inversely proportional to the square of the distance from the source.

Question 9

What is the equation for intensity?

Answer 9

I (Wm-2) = P (W) / 4πx2 (m)

Question 10

What is Stefans law?

Answer 10

P (W) = σAT4

Question 11

What is the wavelength for gamma rays?

Answer 11

10^-12m

Question 12

What is the wavelength for X-rays?

Answer 12

10^-10m

Question 13

What is the wavelength for ultraviolet light?

Answer 13

10^-8m

Question 14

What is the wavelength for visible light?

Answer 14

4 to 7x10^-7m

Question 15

What is the wavelength for infrared light?

Answer 15

10^-5m

Question 16

What is the wavelength for microwaves?

Answer 16

10^-2m

Question 17

What is the wavelength for radio waves?

Answer 17

10^2m

Question 18

What is the general trend across the electromagnetic spectrum from gamma to radio?

Answer 18

Decreasing frequency, increasing wavelength.

Question 19

What is the general trend across the electromagnetic spectrum from radio to gamma?

Answer 19

Decreasing wavelength, increasing frequency.

Question 20

What is multi wavelength astronomy?

Answer 20

Observing different objects in space by studying them with telescopes that detect different regions of the EM spectrum.

Question 21

What is the use of X-rays in multi wavelength astronomy?

Answer 21

Observing very hot matter heated up as it spirals towards a black hole (10^6 to 10^8 K).

Question 22

What is the use of ultraviolet light in multi wavelength astronomy?

Answer 22

Observing supernova remnants and hot stars (10^4 to 10^6 K).

Question 23

What is the use of visible light in multi wavelength astronomy?

Answer 23

Observing planets, stars and some satellites (10^3 to 10^4 K).

Question 24

What is the use of infrared light in multi wavelength astronomy?

Answer 24

Observing cool clouds of dust and gas (10 to 10^3 K).

Question 25

What is the use of microwaves in multi wavelength astronomy?

Answer 25

Observing the cosmic microwave background radiation (1 to 10 K).

Question 26

Describe the main features of the spectrum of a star and state where in the star they arise

Answer 26

Continuous spectrum is due to all radiation of all wavelengths being emitted from the surface of the star.
Line absorption spectrum is due to the passage of radiation through the stars atmosphere.