Yr 13 - Astrophysics & Cosmology (5.5.3 - 5.5.5)

Question 1

Colour of a star depends on.

Answer 1

The luminosity of the star.

Question 2

A Black Body

Answer 2

Body that absorbs all wavelengths of EM radiation.
- Can emit all wavelengths of EM radiation

Question 3

Wien’s Displacement law

Answer 3

Peak intensity of radiation is related to surface temperature of star.

Wavelength ∝ 1 / T (inversely proportional)

K = Wien’s Constant (m.K) / Peak wavelength

Question 4

Spectral Class Types for stars

Answer 4

O - Blue - 25,000/50,000 (K)
B - Blue/White - 12,000/25,000 (K)
A - White - 7,500/12,000 (K)
F - Yellow/White - 6,000/7,500 (K)
G - Yellow - 4,500/6,000 (K)
K - Yellow/Red - 3,000/4,500 (K)
M - Red - 2,000/3,000 (K)

Question 5

Relationship between Kinetic energy and Temperature

Answer 5

Ke ∝ Temperature

Question 6

What do hydrogen nuclei fuse to make?

Answer 6

Helium nuclei

Question 7

Size of low mass star (in terms of solar masses)

Answer 7

0.5 - 10 solar masses

Question 8

Whats a continuous spectrum? (Atomic Spectrum)

What are they used to show?

Answer 8

Superimposed image of both absorption & emission line spectrum.

• No visible dark lines because the colour lines from Emission spectrum cover the dark Lines on Absorption spectrum.
• Used to show black body radiation.

Question 9

What is a line spectrum? (Molecular spectrum)

Answer 9

Either Absorption or Emission line spectrum.

Question 10

Absorption line spectrum

Answer 10

Produced by atoms absorbing energy.

• Dark lines on bright background
• Exited atom

Question 11

Emission line spectrum

Answer 11

Produced by atoms releasing energy

• Bright lines on dark background
• Relaxing atom

Question 12

Whats a transmission diffraction grating?

Answer 12

Glass surface with very fine parallel grooves and slits used to produce optical spectra by diffracting transmitted light.

Question 13

What is maxima and minima?

Answer 13

Maxima - Point where 2 crests of troughs off 2 different waves collide to reinforce one-another.

Minima - Point where crest and trough meet and cancel each other out.

Question 14

Ionisation

Answer 14

Where an atom acquires a positive/negative charge by gaining/loosing electrons.

Question 15

Equation including:

• n
• 𝝺
• d
• Sin 𝞡

Answer 15

n 𝝺 = d Sin𝞡

n = Order of maximum
𝝺 = Wavelength of incident light
d = Slit Seperation
Sin𝞡 = angle beam makes with diffraction grating

Question 16

Wien’s displacement law

Answer 16

Maximum wavelength is inversely proportional to temperature (Kelvin)

Question 17

Stefans Law

Answer 17

Relates luminosity of a star with its absolute temperature.
Known as Stefans constant.

Question 18

One solar mass

Answer 18

1.99 x 10^30 kg

Question 19

Low mass star

Answer 19

0.5 - 10 solar masses

Question 20

How to elements heavier than iron get created?

Answer 20

Supernova Explosions due to high amounts of energy being released.

Question 21

What range of masses can a core be for it to become a neutron star?

Answer 21

Between Chandrasekhar limit and 3 solar masses

Question 22

What range of masses can a core be for it to become a black hole?

Answer 22

Greater than 3 solar masses