U2.7 Astronomy

Question 1

What is the Doppler effect?

Answer 1

When a wave source is moving the waves in front of it get bunched up together and their wavelength decreases.

The waves behind it spread out and therefore their wavelength increases.

Question 2

What terms describe the Doppler effects for light?

Answer 2

Blue shift - The light in front of the source becomes more blue as the wavelength decreases.

Red shift - The light behind the source becomes more red as the wavelength increases

Question 3

What is the equation for observed frequency?

Answer 3

ƒ = ( v_w / v_w + v_s ) x ƒ₀

ƒ = observed frequency
ƒ₀ = emitted frequency
v_w = the velocity of waves in the medium
v_s = velocity of the source relative to the medium; positive if the source is moving away from the receiver

Question 4

What is the equation for observed wavelength?

Answer 4

λ = ( 1 + v_s / v_w ) x λ₀

λ = observed wavelength
λ₀ = emitted wavelength
v_w = the velocity of waves in the medium
v_s = velocity of the source relative to the medium; positive if the source is moving away from the receiver

Question 5

What are the equations for the z parameter?

Answer 5

z = ∆λ / λ = v / c

λ = emitted wavelength
∆λ = difference between observed and emitted wavelengths
v = velocity of source in. Observers direction
c = the speed of the waves in the medium

Question 6

What can the z-parameter be also referred to as?

Answer 6

Red shift

Question 7

What is the equation for Hubble’s law?

Answer 7

v = H₀ x d

v = the recessional velocity
d = the distance between earth and the galaxy in question
H₀ = the Hubble parameter

Question 8

What is the equation for the age of the universe?

Answer 8

Time = 1 / H₀ = d / v

Question 9

What is the cosmological Doppler effects?

Answer 9

The shift in light casused by the universe itself expanding.