Core Physics – Energy

L/O :- To understand redshift and Cosmic microwave background radiation

“Why does an untuned TV

buzz?”

Exam Date -

Quick Quiz - What do you remember from last lesson?

• Write out the electromagnetic spectrum from longest to shortest

• Which are the most dangerous EM waves? What can they cause?

• What is the equation for working out the speed of a wave?

• What happens to a light ray when it travels from air through glass? Why does this happen?

• What is diffraction?• What are the 2 different types of wave? Give

an example• How do you work out the pay-back time for

insulation?• What are the pros and cons of wind energy?• How does increasing the volume of a sound

affect the wave?

What do you know about the

universe?

To explain some of the things we observe in the universe we need to think back to the work we have already done

on waves

Which colour of light has the longest wavelength? How do you know?

What would this affect do to light?

What happens to waves when they move away from you? Remember the Doppler effect?

What happens to waves when they move away from you? Remember the Doppler effect?

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Source of light “Spectra”

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If you pass the light through a gas something different is seen…

helium

Some wavelengths of light are absorbed by the gas – an “absorption spectrum”.

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helium

If the light source is moving away the absorption spectra look a little different…

helium

Before

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The absorption lines have all been “shifted” towards the longer wavelength end (red end)…

After

Before

A similar effect happens with sound – this is called “The Doppler Effect”

Hear Doppler Effect

This is called red shift. The faster the light source moves the further its light will be “shifted”

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Light from different stars and from the edge of the universe also shows this “red-shift”. This suggests that everything in the universe is moving away from a single point.

This is the BIG BANG theory

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Red shift summary

Light from other galaxies has a longer _________ than expected. This shows that these galaxies are moving ____ from us very quickly. This effect is seen to a greater extent in galaxies that are _______ away from us. This indicates that the further away the galaxy is, the ______ it is moving.

This evidence seems to suggest that everything in the universe is moving away from a single point, and that this process started around 15 _____ years ago. This is the ____ ________ Theory.

Words to use – faster, away, big bang, billion, wavelength, further

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http://videos.howstuffworks.com/tlc/29803-understanding-cosmic-radiation-background-noise-video.htm

Is space silent?Well that is what we thought but when we

starting listening we realised there is actually a constant hiss in the back ground

This is called Cosmic Microwave Background Radiation (CMBG)

Cosmic Microwave Background Radiation is thought to be responsible for some of the

fuzz and hiss you hear from an untuned TV

Many scientist believe this could be the echo of the ‘big bang’

What have you learnt?

• Can you explain why galaxies moving away from us appear red?

• Do you know what this affect is called

• Do you know what CMBR stands for?

Have the makers of star-trek got the science right?