Unit 2.6 The Universe

What is used to split light into its different wavelength

A diffraction grating

What can line emission spectra identify

Different elements, since the spectra for each element is different and unique

How did scientist identify the chemical composition of stars

They observe the light it emitted through a spectroscope then compare the line absorption spectra with the spectra of known element

What is red-shift

Observation of increase in the wavelength of light caused by the source moving away from the observer

Who observed spectra from distant galaxies to demonstrate red shift

Sir Edwin Hubble

What two thing can be said about the motion and wavelength of emitted light from a galaxy, the further away it is?

The further the galaxy are, the faster it is moving and the greater the observed increase in wavelength there are.

What does red-shift provide evidence for?

• The universe is expanding

• Big bang theory

What does Big Bang theory suggest

The entire universe started from a very small, hot and dense region in space

Compare the observation red-shift of two galaxy, one is further away from the other

• The galaxy that is further away travels faster and have greater red shift

What did scientist observe to provide evidence that the universe is expanding at an ever fast rate

The observed supernova, which suggested that the galaxy are moving away at an ever faster rate

Prior to observation of supernova, what was believe about the rate of expansion of the universe and why

• The rate of expansion was expected to occur at an ever slower rate.

• It was thought that the gravitational forces would cause the rate of expansion to slow down

What does CMBR stand for

Cosmic Microwave Background Radiation

What does CMBR provide further evidence for

• The Big Bang theory

• CMBR comes from the radiation produced in the Big Bang

How does the existence of CMBR support the expansion of the universe

It is thought that gamma radiation was released in the Big Bang, the expansion of the universe has stretched this radiation, resulting in the microwave radiation present today

How can atomic spectra can be used to identify elements in stars

• A star emits a continuous spectrum of electromagnetic radiation. This radiation passes through the gases in the star’s atmosphere.

• The atom in the gas absorbs specific wavelength of light. These are shown by a gap in the continuous spectrum. Each gap is called an absorption line and the spectrum is an absorption line spectrum.

• Each different elements absorb different wavelength of radiation, depending on its atomic structure. So each element has its own unique absorption lines.

• By looking at the position of the line in the star’s spectrum, you can work out what chemical are present in the star’s atmosphere.