AQA A Level Physics Paper 3 Section B: Astrophysics June 2018 question paper 7408/3BA

The Griffith Observatory in Los Angeles includes an astronomical refracting telescope (Griffith telescope) with an objective lens of diameter 305 mm and focal length 5.03 m

Calculate the wavelength of light for which the Griffith telescope has a minimum angular resolution of 1.8 × 10⁻⁶ rad

The Griffith telescope is used to observe two point objects which subtend an angle of 1.8 × 10^–6 rad at the unaided eye.

The typical human eye has a minimum angular resolution of approximately

Calculate the focal length of the eyepiece lens so that an observer can just resolve the two objects when observing them through the Griffith telescope.

The asteroid Apophis has a diameter of 325 m

It has been calculated that, in 2029, its distance of closest approach to the Earth’s

The Griffith telescope may be used to view Apophis using the eyepiece calculated in question 01.2

Deduce whether this telescope is suitable to obtain a detailed view of Apophis. Support your answer with a calculation.

Sketch, on the axes in Figure 1, the black-body radiation curve for a typical star.

Explain, with reference to the SI units involved, how the curve you have drawn can be used to determine the black-body temperature of the star.

Two stars, 61 Cygnus A and 61 Cygnus B, can be seen very close together in the constellation Cygnus. Early astronomers were unsure whether the two stars form a binary system, or simply appear in the same line of sight. Table 1 shows some of the properties of the two stars.

Evaluate whether the data support the suggestion that the two stars form a binary system.

In your answer you should

• compare the two stars as seen by an observer on Earth

• support your evaluation with suitable calculations.

What is the spectral class of 61 Cygnus A? Tick (✓) the correct box.

Describe the links between galaxies, black holes and quasars.

At a distance of 5.81 × 10⁸ light year, Markarian-231 is the closest known quasar to the Earth. The red shift z of Markarian-231 is 0.0415

Use these data to estimate an age, in seconds, of the Universe.

A typical quasar is believed to be approximately the size of the solar system, with a power output similar to that of a thousand galaxies.

Estimate, with reference to the inverse-square law, how much further the most distant visible quasar is likely to be compared to the most distant visible galaxy.

Evidence to support the Big Bang theory comes from cosmological microwave background radiation and the relative abundance of hydrogen and helium in the Universe.

Explain what is meant by cosmological microwave background radiation and how its existence supports the Big Bang theory.

Explain how the relative abundance of hydrogen and helium supports the Big Bang theory.