U2.7 Astronomy

Question 1

What is the Doppler effect

Answer 1

The apparent change in frequency when there is relative motion between the source and the observer.

Question 2

What is red shift

Answer 2

The lights wavelength is either shortened (blue shifted) because the object is giving off light moving towards the observer, or lengthened (red shifted) because the object is moving away from the observer.

Question 3

What is cosmological red shift

Answer 3

Produced by the expansion of space itself and not from the motion of individual bodies. The wavelength is lengthened as the light travels through the expanding space.

Question 4

What are the classical equations for Doppler shift

Answer 4

f = (v_w / v_w + v_s) f₀

λ = (1 + v_s / v_w) λ₀

f = observed frequency
λ = observed wavelength
v_w = velocity of waves in the medium
v_s = velocity of the source relative to the observer

Question 5

What is the red shift parameter equation

Answer 5

z = Δλ / λ = v / c

λ = emitted wavelength
Δλ = difference between observed and emitted wavelengths
v = velocity of source in the observer’s direction
c = speed of waves in the medium

Question 6

Hubbles law equation

Answer 6

v = H₀d

v = the recessional velocity
d = the distance between earth and the galaxy
H₀ = the Hubble constant