5.5 The Expanding Universe

Question 1

What is meant by the term quasar?

Answer 1

quasi-stellar radio source

Question 2

State two characteristics of a quasar.

Answer 2

any two from
large luminosity 
great distance away 
large red-shift 
large recessional speed 
black hole at centre 
very old

Question 3

Explain what is meant by red shift and why it gives evidence for the Big Bang theory.

Answer 3

increase of wavelength of light towards red end
of spectrum
from distant galaxies
shows recession (consistent with the big bang)

Question 4

Explain what is meant by dark matter

Answer 4

mass/matter that is difficult to detect/does not interact with
other matter
except by gravity

Question 5

Explain why the study of dark matter is important to the understanding of the fate of the
Universe.

Answer 5

idea that fate of universe depends on mass
if sufficient mass- big crunch
if insufficient mass-continued expansion

Question 6

What is the origin of Cosmic Microwave Background Radiation?

Answer 6

(radiation produced soon) after big bang

Question 7

Explain why Cosmic Microwave Background Radiation has a peak wavelength in the microwave region.

Answer 7

Originally high energy or short wavelength
Increase in wavelength eg cooling or expansion
of universe
Wavelenght appropriate to current temperature of universe

Question 8

Explain how red shift is consistent with the movement of distant astronomical objects away from us.

Answer 8

Doppler effect
Expansion of the universe/ Big bang
Wavelength increased
Successive ‘peaks’ of wave emitted at increasing distance from earth

Question 9

The recession speed of a galaxy can be measured by comparing its emission spectral lines with those from an equivalent light source on Earth. Explain why this comparison enables the recession speed to be calculated and describe how the measurements are used to find the recession speed.

Answer 9

Doppler effect
Red shift
Measurement of wavelength or frequency
Giving longer wavelengths/lower frequencies than on Earth
Shift formula

Question 10

What is blue shift and red shift?

Answer 10

A blueshift is any decrease in wavelength, with a corresponding increase in frequency, of electromagnetic waves; the opposite effect is referred to as redshift. In visible light, this shifts the colour from the red end of the spectrum to the blue end.