CAIE IGCSE Physics Universe Redshift and Hubble Law Questions

Practise interpreting redshift, supernova brightness and cosmic microwave background evidence, then apply Hubble's law to recession and Universe-age calculations.

Exam points

use supernova brightness for galaxy distance and wavelength redshift for recession speed
apply H_0 = v/d to calculate recession speed, distance or the Hubble constant with consistent units
use age ≈ 1/H_0 and explain redshift or cosmic microwave background as Big Bang evidence

Covered syllabus points

6.2.3.1—Milky Way is one of many billions of 6.2.3.2—Redshift as an increase in the 6.2.3.3—Light emitted from distant galaxies 6.2.3.4—Redshift in the light from distant 6.2.3.5—Microwave radiation of a specific 6.2.3.6—The CMBR was produced shortly after 6.2.3.7—Speed v at which a galaxy is moving 6.2.3.8—Distance d of a far galaxy can be 6.2.3.9—Hubble constant H0 as recession speed 6.2.3.10—Current estimate for H0 is 2.2 × 10–18 6.2.3.11—D/v = 1/H0 estimates the age of the

[Maximum number: 1]

What is the approximate diameter of the Milky Way?

100000 kilometres

1000000 kilometres

100000 light-years

1000000 light-years

[Maximum number: 6]

A galaxy is approximately $1.2 \times 10^{26} \mathrm{~m}$ from the Earth.

(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 ]

(b)

State the current estimate for the Hubble constant $H_{0}$ .

H_{0}=

[ 1 ]

( $H_{0}=$ ) $2.2 \times 10^{-18}$ per second

B1

(c)

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

speed =

[ 2 ]

$2.6 \times 10^{8} \mathrm{~m} / \mathrm{s}$

A2

$H_{0}=v / d \mathbf{O R}(v=) H_{0} d \mathbf{O R}(v=) 1.2 \times 10^{26} \times 2.2 \times 10^{-18}$

C1

(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 ]

[Maximum number: 4]

(a)

Hydrogen in a very distant galaxy emits electromagnetic radiation which is observed on the Earth.

Scientists on the Earth measure the wavelength of the radiation from the very distant galaxy. The wavelength is 918 nm .

On the Earth, hydrogen in the laboratory emits electromagnetic radiation of wavelength 656 nm .
Name the effect that the scientists observe and state what this shows about the very distant galaxy.

[ 2 ]

(b)

Table 9.1 shows a wavelength of electromagnetic radiation from hydrogen observed in the laboratory and from three galaxies.

The galaxies are at different distances from the Earth.

Table 9.1

Describe what Table 9.1 shows about the motions of the galaxies and state what this suggests is happening to the Universe.

[ 2 ]

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Covered syllabus points

6.2.3 The Universe question 1

6.2.3 The Universe question 2

Question (a)

Question (b)

Question (c)

Question (d)

6.2.3 The Universe question 3

Question (a)

Question (b)