Edexcel ScienceiGCSE Physics

T. Cosmology2019-2020

Name:________________Physics Teacher:______________

House CG

Specification Checklist

Year 11

8.13 describe the past evolution of the universe and the main arguments in favour of the Big Bang

8.14 describe evidence that supports the Big Bang theory (red-shift and cosmic microwave background (CMB) radiation)

8.15 describe that if a wave source is moving relative to an observer there will be a change in the observed frequency and wavelength

8.16 use the equation relating change in wavelength, wavelength, velocity of a galaxy and the speed of light:

Change∈Wavelengthreferencewavelength

= velocity of agalaxyspeed of light

λ− λ0λ0

= Δ λλ0

= vc

8.17 describe the red-shift in light received from galaxies at different distances away from the Earth

8.18 explain why the red-shift of galaxies provides evidence for the expansion of the universe

Cosmology – Science (Physics) 2

Key Words

Key Word Image Definition

Black Dwarf A black dwarf is a white dwarf that has cooled sufficiently that it no longer emits significant heat or light

Black Hole A region of space having a gravitational field so intense that no matter or radiation can escape

Comet A celestial object consisting of a nucleus of ice and dust and, when near the sun, a ‘tail’ of gas and dust particles pointing away from the sun

Galaxy A system/collection of millions or billions of stars

Gravitational Field Strength

The strength of gravity on a planet or moon

Gravitational Force

The attraction force between two objects due to their masses

Main sequence star

A star in its main stable period

Nebula A cloud of gas and dust in outer space

Neutron Star A celestial object of very small radius (typically 30 km) and very high density, composed predominantly of closely packed neutrons

Orbit The regularly repeated elliptical course of a celestial object or spacecraft about a star or planet

Orbital Speed The speed at which an object orbits a planet or star

Red Giant A very large star of high luminosity (brightness) and low surface temperature

Satellite An artificial or natural body placed in orbit round the earth or another planet in order to collect information or for communication.

Solar System The collection of eight planets and their moons in orbit round the sun

Star A star is a celestial body that consists of a luminous sphere of plasma held together by its own gravitational field.

Supernova A star that suddenly increases greatly in brightness because of a catastrophic explosion that ejects most of its mass.

Time Period The time for one complete orbit

Universe All of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy

White Dwarf A small very dense star that is typically the size of a planet

Cosmology – Science (Physics) 3

1: Revision of Astrophysics (Stars and Orbits)

Knowledge and Revision Quiz

1. What is the mass of an object that weighs 0.5kN?

……………… (3)

2. What is the law of conservation of energy?

…………………………………………………………………………………………………………………………………………………………………………………… (2)

3. What is the definition of current?

…………………………………………………………………………………………

………………………………………………………………………………………… (1)

4. What is the purpose of the moderator in a Nuclear Reactor?

…………………………………………………………………………………………

………………………………………………………………………………………… (2)

5. A diver is 30m below sea level [density of sea water = 1200 kg/m3]. What pressure

difference do they experience at this depth?

……………… (3)

6. What is the equation for kinetic energy?

…………………………………………………………………………………………

………………………………………………………………………………………… (1)

Score [ /12]

Learning Outcomes:

1. Describe the orbital shapes for planets, moons and comets2. Calculate the orbital speed, radius and time period from the equation:

v=2×π×rT

3. Describe the life cycle of stars (of different masses), making links to forces, temperature and size

Cosmology – Science (Physics) 4

Summary Sheet: Astrophysics [Shell and Remove]

Term Definition

Universe

Galaxy

Solar System

Main Sequence Star

Orbital Time Period

For the equation below, label what each symbol represents in black and note down the units in green.

v=2×π×rT

Sketch a labelled diagram of the orbits for the following celestial objects.

Moon Planet Comet

Complete the following diagram on the life cycle of stars. Colour stars in the correct colour.

Cosmology – Science (Physics) 5

Worksheet: Orbits and Stars

1. Name the force which keeps the Moon in orbit around the Earth. (1)

………………………………………………………………………………………………………

2. Describe how a comet’s orbit differs from that of a planet. (2)

………………………………………………………………………………………………………

………………………………………………………………………………………………………

3. Make a sketch to show the orbit of a comet around the Sun (2)

a. Mark the points on the orbit where the comet has:

i. The most Kinetic Energy (1)

ii. The most Gravitational Potential Energy (1)

b. Add a comet with its tail to the orbit. (1)

4. A satellite has an orbital speed of 3054 m/s. Their orbital radius is 42 000 km.

a. How long does it take the satellite to orbit the Earth once? (3)

……………………….. unit ……………………….

b. Why is this time period useful for communication? (1)

[Hint: Can you convert your time from ‘a’ into days?]

………………………………………………………………………………………………

………………………………………………………………………………………………

5. The various stages of the life cycle of a star like the Sun are listed below.

a. Number them from 1-4 in the order they occur. (2)

Main Sequence Star

White Dwarf

Red Giant

Cosmology – Science (Physics) 6

Protostar

b. In what stage of its life cycle is the Sun now? (1)

………………………………………………………………………………………………

c. What will be the final stage in our stars life cycle? (1)

………………………………………………………………………………………………

6. What process provides the energy for a star to emit its own light? (1)

………………………………………………………………………………………………………

7. What are the two forces which act on a main sequence star to keep it stable? (2)

………………………………………………………………………………………………………

………………………………………………………………………………………………………

8. From this table, identify one of the following types of star, justifying your choice. (6)

a. Red dwarf

………………………………………………………………………………………………

………………………………………………………………………………………………

b. White dwarf

………………………………………………………………………………………………

………………………………………………………………………………………………

c. Red giant

………………………………………………………………………………………………

………………………………………………………………………………………………

Cosmology – Science (Physics) 7

Score [ /25]

2: The Evolution of the Universe and the Big Bang

Knowledge and Understanding QuizUse the knowledge you gained in the previous lesson to answer the following questions.

1. What is the name of the force of attraction between two masses in space?

……………………………………………………………… (1)

2. What is the definition of a Galaxy and can you give an example? ………………………………………………………………………………………… (2)

3. Can you lable the objects in the diagram below?

(4)

4. On Planet A, a mass of 74kg has a weight of 650N. What is the value of ‘g’ on this

planet?

……………… (3)

5. A 500g object is moving at 5 m/s. How much kinetic energy does the object have?

……………… (3)

Score [ /11]

Cosmology – Science (Physics) 8

Sun Planetor or

Learning Outcomes:

1. Describe the evolution of the universe from the hot, dense state after the Big Bang to modern day.

2. Describe what CMBR is. 3. Explain why CMBR supports the theory of the Big Bang

The Evolution of the Universe

Key Ideas

1. Scientists believe the universe started with the Big Bang.2. During the first picosecond (10−12seconds) of cosmic time it is thought that the

currently understood laws of physics may not have applied. It also saw the emergence in stages of the four known fundamental forces.

3. The early universe, lasting around 377,000 years saw the various kinds of subatomic particles are formed in stages.

4. Next came the dark ages (377,000 years until about 1 billion years post Big Bang) during which time the Universe got cold enough for water to form and stars to be born.

5. From 1 billion year until today we saw galaxy’s form and the components of the Universe are much the same as they are today.

6. Astronomers predict that in the far future we will enter the Stelliferous Era when no more stars are born making the Universe darker and darker as it expands.

Cosmology – Science (Physics) 9

Literacy Task: CMBR

Read the article below by Paul A. Heckert and use the information within it to answer the questions.

The Cosmic Background RadiationDiscovery Supporting Big Bang Theory for the Origin of the Universe (Jul 27, 2007)

Paul A. Heckert

Penzias and Wilson accidentally discovered the 3K cosmic microwave background radiation,

which provided strong evidence supporting the big bang theory.

TV Static and the UniverseDisconnect your TV from any cable connection. Tune it to a channel with no station in your

area. Not picking up any signal, you will see a fuzzy non-picture that we commonly call static

or snow. The technical term for this static is noise.

Now imagine attaching your TV to an antenna large enough to pick out even the weakest

signals from all that noise. To further enhance your ability to pick up weak signals, you would

need to eliminate all sources of noise. So, imagine systematically identifying and then

eliminating all possible sources of noise. In the early 1960s, Arno Penzias and Robert

Wilson did just that.

OK! They weren't really using their TV. They did however have a microwave receiver (about

the same wavelength as TV signals) attached to a large horn shaped antenna. Penzias and

Wilson were trying to build a microwave receiver sensitive enough to pick up weak signals

emitted by celestial sources in our Milky Way galaxy.

To pick up the weak celestial signals, Penzias and Wilson worked to eliminate all the noise

from their antenna and receiver. The last stubborn little bit of noise would not go away no

matter what they tried. They even crawled into the antenna, chased away the pigeons

setting up housekeeping there, and removed the nest and what they called a "white

dielectric film" left by the pigeons. All to no avail! The noise was not pigeons or their

droppings. It was still there. It was something bigger.

Perhaps the microwave noise somehow came from nearby New York City. Pointing the

antenna towards the big apple didn't change the noise level. New York was not awash in

microwaves. It was something bigger than the big apple.

Cosmology – Science (Physics) 10

As the Earth turned, their antenna pointed to different parts of the solar system. If the source

of these mysterious microwaves were in the solar system, the strength of this noise should

vary as the Earth turned on its axis. For example if the microwaves somehow originated in

the Sun, the noise level would be higher in the daytime than at night. It wasn't. The noise did

not originate in the solar system. It was something bigger.

The Earth continued its annual journey around the Sun. If the microwaves originated from a

distinct location in our galaxy, the galaxy itself, or perhaps another galaxy, then the noise

level should increase when Earth was on the same side of the Sun as the source of

microwaves. The noise level didn't change, as the Earth orbited the Sun. It was something

still bigger.

Big Bang Theory

Not many things are bigger than a galaxy. Penzias and Wilson were puzzled. At the nearby

Institute for Advanced Study, in Princeton New Jersey, Robert Dicke and his colleagues had

recently concluded that if the big bang theory for the origin of the universe were correct, the entire universe should be awash in a faint microwave glow.

They were even starting to try finding this radiation when they learned that Penzias and

Wilson had scooped them. The microwaves turned out to be what is left, after 10 to 20 billion

years, of the heat from the  big bang . Penzias and Wilson had inadvertently discovered

the big bang. Their mysterious microwaves were not pigeons, New York, the Sun, the Milky

Way, or another galaxy. They were the universe! There isn't something bigger.

GlossaryIn the table below, note down any terms you read but did not understand. Use a dictionary or the internet to find their definitions.

Word Definition

Cosmology – Science (Physics) 11

Questions:

1. What does CMBR stand for? (1)

………………………………………………………………………………………………………

2. What is static noise? (2)

………………………………………………………………………………………………………

………………………………………………………………………………………………………

………………………………………………………………………………………………………

3. Where could the microwave receiver get messages from? (1)

………………………………………………………………………………………………………

………………………………………………………………………………………………………

4. Where did they think the final bit of noise might have come from? (3)

………………………………………………………………………………………………………

………………………………………………………………………………………………………

………………………………………………………………………………………………………

5. How did they know that the noise was not coming from New York? (2)

………………………………………………………………………………………………………

………………………………………………………………………………………………………

………………………………………………………………………………………………………

6. How did they know that the noise was not coming from the Sun? (2)

………………………………………………………………………………………………………

………………………………………………………………………………………………………

………………………………………………………………………………………………………

7. How did they know that the noise was not coming from a nearby galaxy? (2)

………………………………………………………………………………………………………

………………………………………………………………………………………………………

………………………………………………………………………………………………………

8. What did the microwaves turn out to be? (2)

………………………………………………………………………………………………………

………………………………………………………………………………………………………

………………………………………………………………………………………………………

Score [ /15]

Cosmology – Science (Physics) 12

3: Evidence for the Big Bang

Knowledge and Revision Quiz

1. A 200g bird has 50J of gravitational potential energy. How high up must the bird be?

……………… (3)

2. Give 2 sources of background radiation?

…………………………………………………………………………………………………………………………………………………………………………………… (2)

3. What is the definition of a transverse wave?

…………………………………………………………………………………………

………………………………………………………………………………………… (2)

4. Where do alpha, beta and gamma originate from?

………………………………………………………………………………………… (1)

5. How much charge passes a point in a circuit if a 3A current flows for 2 minutes?

……………… (3)

6. A current carrying wire will experience a force when placed in a uniform magnetic

field. What is this effect called?

………………………………………………………………………………………… (1)

Score [ /12]

Cosmology – Science (Physics) 13

Learning Outcomes:

1. Describe what is meant by the term ‘Red Shift’2. Explain why ‘Red Shift’ supports the Big Bang theory and an expanding

universe3. Explain how the amount of ‘Red Shift’ changes for galaxies that are further

away from Earth.

Redshift

Key Ideas

1. When a wave is moving relative to observer there is a change it it’s observed wavelength.

2. When a wave is moving away from us it’s wavelength ‘stretches’ causing it to increase. 3. The longest wavelength of visible light is red.4. When a galaxy emitting visible light is moving away from us it appears to be red. We call

this phenomena red shift.5. The further, the galaxy is from Earth, the faster it is moving away from us. This causes

the galaxy to be red shifted more. 6. Red shift is evidence to support the Big Bang and the theory of an expanding universe.

https://www.youtube.com/watch?v=CMSYv_Z4SI8

Cosmology – Science (Physics) 14

Worksheet: Redshift and the Expanding Universe

The table below shows red-shift data from distant galaxies. Distances are given from Earth in mega parsecs, where one parsec is equal to 3x1016 m (30,000,000,000,000,000 m). The red-shift data is given as a percentage increase in the original wavelength.

Galaxy Distance from Earth (mpc)

Increase in wavelength (% increase on original wavelength)

NGC-5357 0.45 0.07

NGC-3627 0.9 0.22

NGC-5236 0.9 0.17

NGC-4151 1.7 0.32

NGC-4472 2.0 0.28

NGC-4486 1.8 0.27

NGC-4649 2.4 0.36

Using the table above, answer the questions below:

1. Plot a graph of Distance from Earth (y-axis) against Increase in Wavelength (x-axis) and add a line of best fit.

Cosmology – Science (Physics) 15

2. What galaxy shows the largest increase in wavelength?

………………………………………………………………………………………………………

3. Use your graph to predict the distance from earth of a galaxy that shows a red shift of

0.25%?

………………………………………………………………………………………………………

4. What % in wavelength would we expect from a galaxy that is 1.5 mpc away from Earth?

………………………………………………………………………………………………………

If we took the data from a lot more galaxies we get a graph that looks like this:

5. Describe the correlation of the graph.

………………………………………………………………………………………………………

6. What conclusion can you make for the relationship between the distance of a galaxy

from Earth and the red shift observed?

………………………………………………………………………………………………………

………………………………………………………………………………………………………

………………………………………………………………………………………………………

………………………………………………………………………………………………………

Cosmology – Science (Physics) 16

Increase in wavelength (% increase on original wavelength)

Distance from Earth (mpc)

Stretch Tasks

7. The speed that a galaxy is moving at can be found by multiplying the percentage increase in wavelength by the speed of light (300,000,000) and then dividing by a hundred. Fill in the table below with the speed of the galaxies.

Galaxy Speed (m/s)

NGC-5357

NGC-3627

NGC-5236

NGC-4151

NGC-4472

NGC-4486

NGC-4649

8. What conclusion can you make about the speed of galaxies and their distance from

Earth?

………………………………………………………………………………………………………

………………………………………………………………………………………………………

………………………………………………………………………………………………………

………………………………………………………………………………………………………

9. How does this link to your answer to Question 6?

………………………………………………………………………………………………………

………………………………………………………………………………………………………

………………………………………………………………………………………………………

Cosmology – Science (Physics) 17

Worksheet: The Universe and the Big BangUse your existing and new knowledge about Astrophysics to complete the multiple choice below. Circle/highlight the correct answer.

Score [ /10]

Cosmology – Science (Physics) 18

4: The Doppler Equation

Knowledge and Understanding QuizUse the knowledge you have gained in the previous lessons to answer the following questions.

1. In what part of the HR-Diagram would you find the sun?

……………………………………………………………… (1)

2. On Planet T, a mass of 20g has a weight of 6mN. What is the value of ‘g’ on this planet?

……………… (3)

3. If a star appears red in colour what could I say about its temperature?

………………………………………………………………………………………… (1)

4. A satellite orbits the earth with an orbital radius of 8000km. It takes the satellite 2

years to do one complete orbit. What is the orbital speed of the satellite?

……………… (3)

5. Rearrange the equation for orbital speed to make r the subject.

(2)

Score [ /10]

Learning Outcomes:

1. Describe the Doppler Effect and how this can apply to both sound and light. 2. Explain why the frequency of a sound appears to change as it moves past you.

3. Rearrange and use the equation:λ− λ0λ0

= Δ λλ0

= vc

Cosmology – Science (Physics) 19

To calculate the speed at which a star or galaxy is moving relative to us.

The Doppler Equation

Rearranging the Equation

Key Ideas

1. The Doppler equation is:λ− λ0λ0

= Δ λλ0

= vc

2. λ0 is the referencewavelength3. λ is the observedwavelength

Cosmology – Science (Physics) 20

4. v is the volocity of a galaxy5. c isthe speed of light (300000000m /s)

Worked Examples

1. Light is emitted by the Sun and has a wavelength of 434nm. A distant galaxy emits the same light but because of the Doppler Effect it has a wavelength of 483nm. Calculate the speed at which the galaxy is moving relative to Earth.

2. A galaxy is moving away from Earth at a speed fo 42 000km/s. If it is emitting light with a wavelength of 500nm, what will be the observed wavelength of this light on Earth?

3. A distance star is moving away from Earth at a speed of 62 000 km/s. If we observe a wavelength of 620nm, what is the wavelength of light being emitted from the star?

Cosmology – Science (Physics) 21

Worksheet – Orbital Speed

Complete the questions below using the equation you have just learnt. You must show all of your working [equation, substitution, solution and units]

The Doppler Equation is:λ− λ0λ0

= Δ λλ0

= vc

1. Light is emitted by the Sun and has a wavelength of 322nm. A distant galaxy emits the same light but because of the Doppler Effect it has a wavelength of 364nm. Calculate the speed at which the galaxy is moving relative to Earth.

…………………..

2. Light is emitted by the Sun and has a wavelength of 652nm. A distant star emits the same light but because of the Doppler Effect it has a wavelength of 667nm. Calculate the speed at which the star is moving relative to Earth.

………………….

3. Light is emitted by the Sun and has a wavelength of 650nm. A distant Sun emits the

same light but because of the Doppler Effect it has a wavelength of 675nm. Calculate

the speed at which the star is moving relative to Earth.

………………….

Cosmology – Science (Physics) 22

4. A galaxy is moving away from Earth at a speed of 23 000 000m/s. If it is emitting light with a wavelength of 452nm, what will be the observed wavelength of this light on Earth?

…………………..

5. A star is moving away from Earth at a speed of 125 000km/s. If it is emitting light with a wavelength of 265nm, what will be the observed wavelength of this light on Earth?

…………………..

6. A distance star is moving away from Earth at a speed of 12 000 000 m/s. If we observe a wavelength of 236nm, what is the wavelength of light being emitted from the star?

…………………..

7. A distance galaxy is moving away from Earth at a speed of 50 000 km/s. If we observe a wavelength of 525nm, what is the wavelength of light being emitted from the galaxy?

…………………..

8. A galaxy is moving away from Earth at a speed of 24 000 000m/s. If it is emitting light with a wavelength of 364nm, what will be the observed wavelength of this light on Earth?

Cosmology – Science (Physics) 23

…………………..

Spectral Lines and Red Shift

Key Ideas

1. Spectra diagrams allow us to see what wavelengths of light are being observed from different galaxies.

2. We call the dark lines absorption lines.3. The lines above are the frequencies of light that have been absorbed by Hydrogen. 4. Ass the galaxies get further away you will notice that due to the Doppler effect the

observed wavelength of light move further to the right (into the red section)5. This is why it is called Red Shift.

Cosmology – Science (Physics) 24

6. A shift of the spectra lines to the right implies that eh wavelength is getting longer, thus the galaxies must be travelling away from us.

Spectral Lines and Red Shift

Using your knowledge from the previous lesson and the equation:

λ− λ0λ0

= Δ λλ0

= vc

can you work out how fast each of the three galaxies above is travelling relative to Earth? [Estimate the scales as best as you can]

1. Nearby Galaxy:

2. Distant Galaxy:

3. Furthest Galaxy:

Cosmology – Science (Physics) 25

More Questions like this can be found on Textbook pages 274-276

Cosmology – Science (Physics) 26

Stretch Worksheet – Star Clusters

The photograph shows the giant galaxy M87, which lies at a distance of 54 million light years from us. In the photograph, you can see some small star clusters which are in orbit around the giant galaxy.

Use your MacBook to do some research to see if you can come up with the answers to the following questions

1. Explain why the star clusters orbit the giant galaxy. Why can the clusters not remain

stationary in space?

…………………………………………………………………………………………………..

…………………………………………………………………………………………………..

…………………………………………………………………………………………………..

…………………………………………………………………………………………………..

…………………………………………………………………………………………………..

…………………………………………………………………………………………………..

2. A star cluster orbits the galaxy with an orbital speed of 560 km/s with an orbital radius

of 120 000 light years. Calculate the time of orbit in millions of years.

Cosmology – Science (Physics) 27

Stretch Worksheet – Yawn and Crunch

The Big Bang and explaining universe are not the only theories associated with our Universe (although they are backed up by the most scientific evidence!).

Two more theories are the ‘Big Yawn’ and the ‘Big Crunch’.

Use your MacBook to do some research these theories and summarise your findings below. Diagrams are encouraged.

BIG YAWN BIG CRUNCH

Cosmology – Science (Physics) 28

Cosmology

Past Paper Questions

Q1. 

(a)  Which of these objects orbits a planet?

(1)

   A    comet

   B    dwarf star

   C    galaxy

   D    moon

Cosmology – Science (Physics) 29

(b)  What is the correct name for our galaxy?

(1)

   A    Crab Nebula

   B    Milky Way

   C    Solar System

   D    Universe

(c)  Which of these objects has the largest mass?

(1)

   A    artificial satellite

   B    comet

   C    Earth

   D    Sun

(d)  Which of these stars is the coolest?

(1)

   A    blue star

   B    orange star

   C    red star

   D    yellow star

 

(Total for question = 4 marks)

 Q2. 

The International Space Station (ISS) is a satellite that orbits the Earth at a height of 409 km above the surface of the Earth.

The ISS has an orbital speed of 7.66 km/s and a period of 92.7 minutes.

(a)  (i)  Calculate the orbital radius of the ISS.

Give your answer to 3 significant figures.

(4)

Cosmology – Science (Physics) 30

orbital radius = ........................................................... km

(ii)  Calculate the radius of the Earth using your value for the orbital radius.

(1)

Earth radius = ........................................................... km

 

(Total for question = 5 marks)

 

Cosmology – Science (Physics) 31

Q3.

(a)  Which of these objects orbits a planet?

(1)

   A    comet

   B    dwarf star

   C    galaxy

   D    moon

(b)  What is the correct name for our galaxy?

(1)

   A    Crab Nebula

   B    Milky Way

   C    Solar System

   D    Universe

(c)  Which of these objects has the largest mass?

(1)

   A    artificial satellite

   B    comet

   C    Earth

   D    Sun

(d)  Which of these stars is the coolest?

(1)

   A    blue star

   B    orange star

   C    red star

   D    yellow star

 (Total for question = 4 marks)

Cosmology – Science (Physics) 32

 Q4.

This question is about astrophysics.

(a)  (i)  What is a star formed from?

(1)

   A    a black dwarf

   B    a nebula

   C    a planet

   D    a white dwarf

(ii)  Which of these indicates that the Universe is expanding?

(1)

   A    galaxies are moving further away from each other

   B    galaxies rotate

   C    it takes millions of light years for light to reach us from some stars

   D    some stars in the Milky Way are accelerating towards our Sun

(iii)  Which of these provides evidence for the Big Bang theory?

(1)

   A    cosmic microwave background radiation

   B    nebulae

   C    neutron stars

   D    ultrasound radiation

(iv)  Which of these does red-shift provide evidence for?

(1)

   A    galaxies are moving away from each other

   B    nebulae contract to form stars

   C    red giants shrink to red dwarfs

   D    white dwarfs expand into red giants

Cosmology – Science (Physics) 33

(b)  The spectra of stars and galaxies show lines at specific wavelengths that correspond to the spectra of hydrogen, helium and carbon.

Give reasons why lines corresponding to these elements are found in spectra from typical galaxies.

(2)

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

(c)  The spectrum of light from an astronomical object called a quasar can be compared to the spectrum of hydrogen on Earth.

(i)  Calculate the change in wavelength, Δλ, for the line at the red end of the spectrum.

(2)

Δλ = ........................................................... nm

(ii)  Calculate a value for the recessional velocity of the quasar using your value for Δλ.

speed of light in free space, c = 3.0 × 105 km/s

(3)

recessional velocity = ........................................................... km/s

Cosmology – Science (Physics) 34

(d)  An astronomer observes the light from a nearby galaxy.

She notices that the spectra for hydrogen from the right side and left side of the galaxy are different.

Explain what information the two spectra give about the movement of the galaxy.

(3)

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

 

(Total for question = 14 marks)

 

Cosmology – Science (Physics) 35

Q5. 

Main sequence stars can vary in brightness, colour and mass.

Describe the evolution of both low mass stars and high mass stars after they join the main sequence.

(6)

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.............................................................................................................................................

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(Total for question = 6 marks)

Cosmology – Science (Physics) 36

Cosmology

Spec Point Notes

Cosmology Specification Notes

8.13 describe the past evolution of the universe and the main arguments in favour of the Big Bang

Scientists believe that about 14 billion years ago all matter in the Universe was in one extremely tiny and dense place. It then suddenly exploded, and has been expanding ever since. This expansion is shown by the red-shift of galaxies and the energy of the explosion can be seen everywhere in the Universe as the CMBR.

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8.14 describe evidence that supports the Big Bang theory (red-shift and cosmic microwave background (CMB) radiation)

If we examine the light spectra for distant galaxies we can see that the wavelengths of the light have become longer. We call this stretching of the waves ‘red-shift’. It tells us that the galaxies producing the light are moving away from us .The further away a galaxy is, the greater its red-shift, so it is moving even faster. This is evidence that the Universe is expanding and so it supports the Big Bang Theory.Microwave radiation canbe detected EVERYWHERE in the Universe. These are the stretched remains of high energy gamma radiation that would have been produced in the explosion that created the Universe. They have stretched because the Univerwse is expanding.

8.15 describe that if a wave source is moving relative to an observer there will be a change in the observed frequency and wavelength

This is called the Doppler Effect. If something that emits a wave moves whilst it is doing so (imagine a noisy motorbike coming towards you then going further away, emitting sound waves the whole time) then the wavelength of the sound will become shorter as it is moving towards you, increasing the frequency, and stretched as it is moving away, decreasing the frequency.You will hear this as a change in pitch, getting higher as it approaches and lower as it moves away. The same thing happens for a moving object that is emitting light waves –eg a galaxy

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8.16 use the equation relating change in wavelength, wavelength, velocity of a galaxy and the speed of light:

8.17 describe the red-shift in light received from galaxies at different distances away from the Earth

The further away a galaxy is the greater its red-shift and hence the faster it is moving away from us.

8.18 explain why the red-shift of galaxies provides evidence for the expansion of the universe

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More distant galaxies have greater red-shift and therefore are receding faster because the space between all galaxies is stretching as the universe expands.

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