2.7 Astronomy

Question 1

Does a fire engine ahve a bigger/smaller pitch when it comes towards us?

Answer 1

Bigger pitch because it has a smaller wavelength (Doppler)

Question 2

What is the Doppler shift used by some traffic police for?

Answer 2

To find the speed of passing motorists

Question 3

How can the Doppler shift find the speed of passing motorists

Answer 3

The machine transmits microwave signal of known frequency and then records 8the frequency of the echo received from target vehicle
The greater the difference between frequencies , greater speed of target vehicle

Question 4

blue-shifted

Answer 4

When the lights wavelength is shortened because the object is moving away from the observer

Question 5

Red-shifted

Answer 5

When the lights wavelength is lengthened because the object is moving away from the observer

Question 6

How did Edwin Hubble conclude that stars in the galaxies are moving away from earth

Answer 6

The spectral lines from hydrogen of different stars corresponded to hydrogens emission spectrum but were slightly longer

Question 7

What is the cosmological red shift

Answer 7

Light waves from different galaxies are being stretched as the space between us and that galaxy increases

Question 8

What is Hubbles Law?

Answer 8

A graph of recessional velocity against distance is a straight line thru the origin, indicating direct proportion and proof of the universe expanding