CAIE IGCSE Physics 6.2.3 The Universe Topic Practice

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Covered syllabus points

6.2.3.1—Milky Way is one of many billions of6.2.3.2—Redshift as an increase in the6.2.3.3—Light emitted from distant galaxies6.2.3.4—Redshift in the light from distant6.2.3.5—Microwave radiation of a specific6.2.3.6—The CMBR was produced shortly after6.2.3.7—Speed v at which a galaxy is moving6.2.3.8—Distance d of a far galaxy can be6.2.3.9—Hubble constant H0 as recession speed6.2.3.10—Current estimate for H0 is 2.2 × 10–186.2.3.11—D/v = 1/H0 estimates the age of the

Question 1

[Maximum number: 1]

What is the approximate diameter of the Milky Way?

A

100000 kilometres

B

1000000 kilometres

C

100000 light-years

D

1000000 light-years

Question 2

[Maximum number: 6]

A galaxy is approximately 1.2×1026 m1.2 \times 10^{26} \mathrm{~m} from the Earth.

Question (a)

(a)

Scientists observe light from the distant galaxy.

The wavelength of the observed light is longer than the wavelength of the light emitted from the galaxy.

State the name of this effect.

[ 1 ]

Question (b)

(b)

State the current estimate for the Hubble constant H0H_{0}.

H0=H_{0}=
[ 1 ]

Question (c)

(c)

Calculate the speed at which the galaxy is moving away from the Earth.

speed =
[ 2 ]

Question (d)

(d)

Scientists have measured the speeds at which distant galaxies are moving away from the Earth and their distances from the Earth.

These measurements suggest that all the Universe was once at a single point.
Explain why.

[ 2 ]

Question 3

[Maximum number: 4]

Question (a)

(a)

Light observed from distant galaxies is redshifted.

State the theory of the Universe that this observation supports.

[ 1 ]

Question (b)

(b)

Cosmic microwave background radiation (CMBR) is observed at all points in space.

[ 3 ]

Question (i)

(i)

State when this radiation was produced.

[ 1 ]

Question (ii)

(ii)

Explain why this radiation is now in the microwave region of the electromagnetic spectrum.

[ 2 ]
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