AS2 2.7 Astronomy

Question 1

What is the Doppler Effect?

Answer 1

The apparent change in the frequency/wavelength of a wave when there is relative motion between the source and the observer.

Question 2

What are the doppler Shift equations?

Answer 2

F = (Vw / Vw + Vs) x Fo
λ = (1 + Vs/Vw) x λo

F = observed frequency

Vw = velocity of the waves in a medium

Vs = the velocity of the source relative to the medium

Fo = the frequency emitted from the source

λ = the observed wavelength

λo = the wavelength emitted from the source

Question 3

What happens to the wavelength if the source is moving towards the observer?

Answer 3

λ < λo

Question 4

What happens to the wavelength if the source is moving away from the observer?

Answer 4

λ > λo

Question 5

what happens to the Velocity of the source relative to the medium if the source moving towards the observer?

Answer 5

Vs = negative

Question 6

what happens to the Velocity of the source relative to the medium if the source moving away from the observer?

Answer 6

Vs = positive

Question 7

What effect does the doppler shift have on sound waves?

Answer 7

the pitch increases or decreases

Question 8

what effect does the doppler shift have on light waves?

Answer 8

the colour is red-shifted / violet-shifted

Question 9

What is the cosmological Red Shift?

Answer 9

Cosmologists think of the expanding universe as the expansion of space itself. so light waves from a distant galaxy are being stretched as the space between us and that galaxy increases. This is called the cosmological red shift to distinguish it from the red shift produced by sources that are moving through space.

Question 10

What is the difference between Cosmological Red Shift and Doppler Shift?

Answer 10

Doppler shift is due to the relative speed between the observer and the source. Cosmological Red Shift is due to the expansion of the space between the observer and the source.

Question 11

What is the Red Shift Parameter equation?

Answer 11

Z = (Δλ / λo) = (Δf / fo) = (V / c)

Z = the red shift parameter

Δf = difference between the emitted and observed frequency
fo = the emitted frequency

Δλ =the difference between the observed and emitted frequency
λo = the emitted frequency

V = the velocity of the source in the observer’s direction
c = the usual speed of the waves in a medium

Question 12

What is the equation for Hubble’s Law?

Answer 12

V = Ho x d

V = recessional velocity/ ms^-1
Ho = Hubble’s parameter/ constant (Ho = 2.4 x 10^-18 s)
d = distance between the Earth and galaxy in question.

Question 13

What is the equation for the age of the universe?

Answer 13

T = 1 / Ho