Transcript 17. The Universe - science
The Doppler effect
24 April, 2020
Objectives
Be able to describe what the Doppler effect is.
HSW: AF1 – Thinking scientifically, using models to explain scientific phenomena.
Used before in: Will use again in:
PLTS: Creative thinkers:
ask questions to extend their thinking
.
Used before in: Will use again in:
Keywords
Wavelength, frequency, Doppler, Redshift, Hubble, speed © Boardworks Ltd 2006 1 of 38
OUTCOMES • ALL MUST be able to desscribe how wavelength effects the pitch of a sound.
• MOST SHOULD be able to describe what the Doppler effect is and a situation where the Doppler effect occurs. • SOME COULD be able to.
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5 Question Quick Revision Quiz
1) The unit of measurement for Frequency is a) Newtons (N) b) Hertz (Hz) c) Pascals (P) d) Amps (A) 3 2 1 4 2) Which number shows the amplitude of a wave?
3) Which number shows the wavelength of a wave?
4) What is meant by the frequency of a wave? 5) The higher the frequency of a sound, the higher the pitch. True or False?
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The Doppler effect 4 of 38 © Boardworks Ltd 2006
The Doppler effect
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• Doppler Ball
Demo Time
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Doppler effect
• You tube link – STOP AT 9 minutes as it goes into A Level explanation at this point.
• http://www.youtube.com/watch?v=w6yH22 qRyj0&feature=related © Boardworks Ltd 2006 7 of 38
• Worksheet
Doppler effect
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2.
When an automobile moves towards a listener, the sound of its horn seems relatively a. Low pitched b. High Pitched c. Normal When the automobile moves away from the listener, its horn seems a. Low pitched b. High Pitched c. Normal 3.
4.
5.
The changed pitch of the Doppler effect is due to changes in a. Wave speed b. wave frequency Circle the letter of each statement about the Doppler Effect that is true. a.
It occurs when a wave source moves towards an observer b.
c.
d.
It occurs when an observer moves towards a wave source It occurs when a wave source moves away an observer It occurs when an observer moves away a wave source True / False: A moving wave source does not affect the frequency of the wave encountered by the observer. 6.
True / False: A higher frequency results when a wave source moves towards an observer. 7.
Two fire trucks with sirens on speed towards and away from an observer as shown below. A) Which truck produces a higher than normal siren frequency? B) Which truck produces a lower than normal siren frequency? 8.
Describe why an ambulance changes pitch as it drives past you. Use a series of diagrams if you prefer. Use these key words in your answer: Wavelength, compressed, expanded, frequency/pitch © Boardworks Ltd 2006
Plenary
Long
Low
Pitch
Away Towards 10 of 38 Wavelength
High
Frequency Short © Boardworks Ltd 2006
24 April, 2020
Redshift and the Big Bang
Objectives
Be able to describe what the Doppler effect is.
HSW: AF1 – Thinking scientifically, using models to explain scientific phenomena.
Used before in: Will use again in:
PLTS: Creative thinkers:
ask questions to extend their thinking
.
Used before in: Will use again in:
Keywords
Wavelength, frequency, Doppler, Redshift, Hubble, speed © Boardworks Ltd 2006 11 of 38
OUTCOMES
• ALL MUST be able to describe what the Doppler effect is.
• MOST SHOULD be able to relate the Doppler effect in Sound to the Redshift of Light. • SOME COULD be able to explain how Redshift can be used to measure the distances of cosmic objects and ask questions about our knowledge of the universe.
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• How did we get here?
• We are not sure but the theory of the Big Bang has evidence to support it (redshift) and supports other findings that have been made (Cosmic background radiation) © Boardworks Ltd 2006 14 of 38
Evidence: •
2 main pieces of evidence to back up The Big Bang Theory:
•
1
Galactic Redshift (Hubble’s Law) • 2 Cosmic Microwave Background Radiation
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Passing white light through a prism (revise) 16 of 38 © Boardworks Ltd 2006
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Emission Spectra
• Light from galaxies and stars split by a prism appears as a spectrum of colours © Boardworks Ltd 2006
24/04/2020 If the light source is moving away the absorption spectra look a little different…
Before After
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The absorption lines have all been “shifted” towards the longer wavelength end (red end)…
Before
This is called red shift. The faster the light source moves the further its light will be “shifted” 24/04/2020 19 of 38
After
A similar effect happens with sound – this is called “The Doppler Effect” © Boardworks Ltd 2006
The Doppler effect in space
In the same way that a sound moving away from an observer is lower in frequency the light we observe from distant galaxies is shifted more towards the red, low frequency end of the spectrum.
This means the distant galaxies are moving away from us.
It has also been observed that the further the galaxy is away, the greater the amount of red shift. This means that these very distant galaxies are moving faster than the galaxies closer to us, indicating that the universe is expanding.
How can we use this information to measure the distances of galaxies and stars? Watch this youtube clip.
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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 21 of 38 © Boardworks Ltd 2006
Hubble’s Law – Redshift and distances
http://www.youtube.com/watch?
v=IwMFBqzpxDU 22 of 38 © Boardworks Ltd 2006
Speed of movement away
Hubble’s Law
Straight line R T Nuttall 23 of 38 Churston Ferrers Distance © Boardworks Ltd 2006
Practical time!!
• Slinky demo • & • Class balloon experiment – make a balloon like the one in the clip to show an expanding universe • Draw a series of diagrams of either of these models and describe how help to explain the Redshift of Stars and Galaxies.
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Redshift
Redshift and distance Try to explain to the person sat next to you how redshift can be used to find the distance of objects.
HINT
– answer these q’s to help Are all galaxies moving away from us?
How do we know?
Which ones are moving fastest?
So how can we use this information to measure distance?
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Plenary - Hotseat
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24 April, 2020 Cosmic Microwave Background Radiation
Objectives
Be able to describe how Cosmic Microwave Background Radiation backs up the theory of the Big Bang.
HSW: AF1 – Thinking scientifically, using models to explain scientific phenomena.
Used before in: Will use again in:
PLTS: Creative thinkers:
ask questions to extend their thinking
.
Used before in: Will use again in:
Keywords
Redshift, Hubble, speed, Microwave, EM-Spectrum © Boardworks Ltd 2006 27 of 38
OUTCOMES
• ALL MUST be able to describe that there was an immense amount of energy in the form of waves at the time of the big Bang.
• MOST SHOULD understand that if Gamma Rays are stretched, they will turn into other types of wave – like Microwaves. • SOME COULD explain how the Cosmic Microwave Background Radiation is evidence that supports the theory of the Big Bang.
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Cosmic Microwave Background Radiation • Watch Stephen Hawking – YouTube clip: http://www.youtube.com/watch?v=-dR 26JmmaBM • Cosmic Microwave Background is energy left over from the Big Bang.
• In the Big explosion ………. radiation was given off.
• Over time this has ………. and has now become that can be picked up on a tv.
Radiation Gamma stretched microwaves © Boardworks Ltd 2006 29 of 38
Image to the edges of the Universe 30 of 38 © Boardworks Ltd 2006
Guided Reading
• Use the worksheet to help you gather the information from the sheet to read on the Big Bang and CMBR 31 of 38 © Boardworks Ltd 2006
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The fate of the Universe
OPEN
Universe continues to expand
CRITICAL
Universe
just
continues to expand Size of Universe
CLOSED
Universe collapses “Big Crunch ” © Boardworks Ltd 2006
The Universe from beginning to end
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Space Project -
DEADLINE: ________.
Evidence for the Big Bang
• You will create a revision resource (booklet or series of posters) that cover the following topics and answer the following questions:
Big Bang
• What is the Big Bang Theory?
Redshift
• What is the Doppler effect?
• What is RedShift?
• How does Redshift provide evidence for the Big Bang?
CMBR
• What is the Cosmic Microwave Background?
• How was it discovered?
• How does it back up the Big Bang theory?
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