Astrophysics 12 - Doppler Effect and Red Shift

Define the Doppler Effect.

The apparent change in frequency of a wave due to the relative velocity of the reciever and emitter.

What is the percieved change in frequency when the reciever and emitter are moving away?

The frequency appears lower.

What is the percieved change in frequency when the reciever and emitter are moving closer?

The frequency appears higher.

When does red shift occur?

When a luminous body is moving away from earth.

When does blue shift occur?

When a luminous body is moving away from the earth.

What is the change in frequency dependent on?

The relative velocity parallel to the line between the emitter and reciever.

Define recessional velocity.

The relative velocity of an object moving away from us.

Give the equation for red shift.

red shift = -(recessional velocity) / speed of light

z = -v / c

When a star is moving away from us, what happens to its absorbtion spectrum?

The entire thing is red-shifted by the same amount.

Give the equation for red shift in terms of frequency of light.

Red shift = -ve change in frequency / original frequency

z = -Δf / f

(where Δf = f - f_obs)

Give the equation for red shift in terms of wavelength

Red shift = change in wavelength / original wavelength

z = Δλ / λ

(where Δλ = λ - λ_obs)