Topic 8 - The Universe

What happens to a light when passed through a prism?

It splits into its seven colours knows as a spectrum.

What was found on the spectrum when the light from the Sun was passed through a prism?

Dark lines appeared at certain wavelengths of light (colours).

What is an absorption spectrum?

A spectrum where dark lines appear because specific wavelengths (colours) of light have been absorbed.

What causes the dark lines on an absorption spectrum?

The gases in the atmosphere of the star have absorbed different wavelengths of light.

How can an absorption spectra be used to identify gases?

Every gas absorbs different wavelengths of light and therefore creates a unique absorption spectrum.

What was absorption spectra used for in the early 19th century?

to study the composition of stars.

How is the absorption spectra from distant stars different from the spectra of the Sun?

The dark lines have moved slightly toward the ‘redder’ wavelengths.

What is Red Shift?

The effect of the dark lines on an absorption spectra shifting towards the red end of the spectrum.

What is the Doppler Effect?

The effect of an increasing wavelength when an object moves away from you or a decreasing wavelength when an object moves toward you.

What does red shift tell us about distant stars?

they are moving away from us.

What is causing the red shift?

The light stretches as it travels through space to the earth.

What theory does red shift support?

The Big Bang Theory.

What is the big bang theory?

The idea that the universe started from a point in space that exploded and the universe is still expanding today.

How does red shift explain the big bang theory?

Red shift suggests the universe is expanding, if time is reversed then all matter came from one point in space.

What is Hubble’s law?

The further away the galaxy, the more red shift is observed.

What two pieces of evidence are there for the big bang theory?

Red shift in absorption spectra and cosmic microwave background radiation (CMBR).

What is cosmic microwave background radiation?

Microwaves that fill our Universe.

Where has cosmic microwave background radiation come from?

Huge amounts of energy (gamma rays) were formed during the big bang. Red shift has caused the gamma rays to stretch and become microwaves.