Edexcel International A Level Physics
Edexcel International A Level Physics Astrophysics and Cosmology Exam Questions
Free Edexcel International A Level Physics exam questions for Astrophysics and Cosmology, with a mark scheme for every pack. Covers gravitational fields, Newton's law of gravitation, black body radiation, stellar luminosity, the H-R diagram, distance measurement, redshift and Hubble's law.
Astrophysics and Cosmology exam questions
1 question pack of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About Edexcel International A Level Physics Astrophysics and Cosmology
Astrophysics and cosmology is part of Unit 5: Thermodynamics, Radiation, Oscillations and Cosmology in Edexcel International A Level Physics. It begins with gravitational fields and Newton's law of gravitation, then applies black body radiation laws to stars. You use the Stefan-Boltzmann law, Wien's law and the inverse square law for intensity, interpret the Hertzsprung-Russell diagram and stellar life cycles, and measure distances using parallax and standard candles. The topic ends with redshift, Hubble's law and the age and fate of the universe. Examiners often combine several of these equations in one problem, such as finding a star's radius.
What you need to know
- Gravitational fields g = F/m and, for a point mass, g = GM/r^2. Newton's law F = Gm1m2/r^2. Gravitational potential Vgrav = -GM/r. Compare gravitational fields with electric fields.
- Black body radiation Stefan-Boltzmann law L = σAT^4 and Wien's law λmaxT = 2.898 × 10^-3 m K. Intensity I = L/4πd^2.
- H-R diagram Luminosity against temperature (temperature increasing to the left). Know main sequence stars, red giants, white dwarfs and the life cycles of stars of different masses.
- Distance measurement Trigonometric parallax for nearby stars; standard candles of known luminosity for more distant objects.
- Redshift and Hubble's law z = Δλ/λ ≈ Δf/f ≈ v/c for v much less than c. Hubble's law v = H0d; the age of the universe is about 1/H0. The fate of the universe depends on its density, and dark matter is part of this uncertainty.
Common mistakes in Astrophysics and Cosmology
- Using °C instead of K in Stefan's or Wien's law.
- Using the star's radius instead of its surface area 4πr^2 in L = σAT^4.
- Drawing temperature increasing to the right on the H-R diagram.
- Using distance from the surface rather than from the centre in Newton's law of gravitation.
- Forgetting to convert km s^-1 Mpc^-1 into s^-1 when using H0.
Try three Astrophysics and Cosmology exam-style questions
1. Calculate the gravitational force between the Earth (5.97 × 10^24 kg) and the Moon (7.35 × 10^22 kg), separated by 3.84 × 10^8 m. (2 marks)
Show the mark scheme answer
F = Gm1m2/r^2 = 6.67 × 10^-11 × 5.97 × 10^24 × 7.35 × 10^22/(3.84 × 10^8)^2; F = 2.0 × 10^20 N.
2. A star has surface temperature 10 000 K and radius 2.0 × 10^9 m. Calculate its luminosity. (2 marks)
Show the mark scheme answer
L = σ4πr^2T^4 = 5.67 × 10^-8 × 4π × (2.0 × 10^9)^2 × (1.0 × 10^4)^4; L = 2.9 × 10^28 W.
3. Explain why a standard candle is needed to measure distances to distant galaxies. (3 marks)
Show the mark scheme answer
Parallax angles are too small to measure for very distant objects; if the luminosity L of an object is known, its measured intensity I can be used; d = √(L/4πI).
Astrophysics and Cosmology FAQs
What does Edexcel International A Level Physics Astrophysics and cosmology cover?
It covers gravitational fields, black body radiation, stellar luminosity and temperature, the H-R diagram, stellar evolution, parallax, standard candles, redshift and Hubble's law.
Which unit is Astrophysics and cosmology examined in?
It is examined in Unit 5: Thermodynamics, Radiation, Oscillations and Cosmology.
What equations do I need for Astrophysics and cosmology?
Learn F = Gm1m2/r^2, g = GM/r^2, V = -GM/r, L = σAT^4, λmaxT = 2.898 × 10^-3 m K, I = L/4πd^2, z ≈ v/c and v = H0d.
