Doppler effect

Question 1

Doppler effect (3)

Answer 1

• The change in wavelength and frequency of a wave as the
  source moves away or towards the observer.
• As the source moves towards the observer, the waves are
  compressed and wavelength decreases
• As the source moves away from the observer, the waves spread out and the
  wavelength increases.

Question 2

Red shift

Answer 2

• increase in wavelength (of em radiation) due to relative
  recessive velocity between observer and source
• red-shift is evidence for the Big Bang as galaxies are redshifted implying that the universe is expanding in all directions

-The more distant the object, the greater its red-shift.

Question 3

binary star systems

Answer 3

where two stars are orbiting a common centre of mass

Question 4

Spectroscopic binaries

Answer 4

are binary star systems in which the stars are too close to be resolved by a telescope, meaning the only way to identify them is by using the Doppler shifts of each star

Question 5

State Hubble’s Law

Answer 5

The velocity of receding galaxies is proportional to their
distance from Earth

Question 6

What is dark energy though to be?

Answer 6

is thought to be the reason behind the universe accelerating.

Question 7

How is dark energy described as and why?

Answer 7

• It is described as having an overall repulsive effect throughout the whole universe
• Since gravity follows the inverse square law, it decreases with distance

Question 8

Why is dark energy controversial?

Answer 8

because there is evidence for its existence but no one knows
what it is or what is causing it.

Question 9

What does it mean when dark energy is constant?

Answer 9

it has a greater effect than gravity and is therefore causing
expansion speed to increase.