AQA A Level Physics Paper 3 Section B: Astrophysics June 2022 question paper 7408/3BA

Draw a ray diagram to show how a converging lens can cause spherical aberration.

Draw a labelled ray diagram for an astronomical refracting telescope in normal adjustment.

Show three non-axial rays passing through both lenses. Label the principal foci of the lenses.

The James Lick telescope is an astronomical refracting telescope. When in normal adjustment, the distance between the lenses of the telescope is 17.4 m and the angular magnification is 750

Calculate the focal length of the eyepiece lens.

The James Lick telescope can be used to identify binary stars.

Two techniques are available using this telescope:

• using a processed image from a CCD, and

• direct observation using the naked eye.

Compare the use of a CCD with the use of the naked eye to observe binary stars with this telescope.

U Cephei is an eclipsing binary system consisting of two stars that orbit their common centre of mass. The primary star is class B; the secondary star is class G.

Figure 1 shows the variation of apparent magnitude of U Cephei with time as observed from Earth.

Explain the shape of the graph in Figure 1.

A particular spectral line has a wavelength of 486.136 nm when measured from a source in the laboratory. This line is also present in the absorption spectrum of the primary star of U Cephei. When observed from Earth, the wavelength of the primary star’s absorption line varies as shown in Table 1.

State why the average of the values in Table 1 is different from the laboratory value.

Show that the orbital speed of the primary star is about 250 km s⁻¹.

Calculate the orbital radius of the primary star.

Which absorption lines would be most prominent in the spectrum of the primary star? Tick () one box.

A different eclipsing binary star system is thought to consist of a white dwarf star and a neutron star.

Discuss how astronomers could confirm this.

C 273 was the first quasar to be discovered. IC 1101 is one of the largest galaxies known. Table 2 shows some information about these objects.

State the property of the quasar that led to its discovery.

Show that the absolute magnitude X of quasar 3 C 273 is about −27

Assume that the quasar and the galaxy are both viewed from the same distance.

Explain which would be the brighter object.

The black hole at the centre of IC 1101 has a mass of 7.1 × 10¹¹ M_S

Calculate the average density within the event horizon of the black hole.

In the middle of the 20th century, there were two competing theories of the Universe. In 1964, electromagnetic radiation was observed coming from all directions in space. Figure 2 shows the distribution of this radiation as observed from Earth.

The graph provides evidence for one of these theories of the Universe.

Discuss the main features of this theory of the Universe.

In your answer, you should include:

• the main predictions and evidence for the theory, and

• a suitable calculation.