IB Physics: Astrophysics Revision

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What does red-shift of distant galaxies show?

Astrophysics is a core part of IB Physics. Revise the key concepts and common mistakes below, then lock them in with the free games.

Key concepts

Light-yearThe distance light travels in one year (~9.5×10¹⁵ m).

Orbital speedv = 2πr ÷ T for a body in a circular orbit.

Main sequence starA stable star fusing hydrogen to helium, gravity balanced by radiation pressure.

Red giant & white dwarfLate stages of a low-mass star's life.

SupernovaThe explosive death of a massive star, leaving a neutron star or black hole.

Red-shiftLight from distant galaxies stretched to longer wavelengths — the universe is expanding.

Learn Astrophysics step by step

Free interactive mini-lessons: short screens, worked examples and quick checks. Pick your exam board to open its course map, then tap L on this topic:

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Common mistakes to avoid

Questions where students often pick the tempting wrong answer — make sure you know the right one:

What does red-shift of distant galaxies show?✗ The galaxies are red-hot. ✓ They are moving away — the universe is expanding.

What is a light-year?✗ A length of time. ✓ A distance — how far light travels in a year.

What happens to a star like the Sun at the end of its life?✗ It explodes as a supernova and forms a black hole. ✓ It becomes a red giant, then a white dwarf.

Practise Astrophysics — free games

Test yourself with these quick revision games for this topic:

▶ Two Truths, One Lie ▶ Reveal Race ▶ Connections Grid ▶ Falling Words ▶ Word Web

See all 22 games in the Revision Arcade →

Astrophysics

Key concepts

Common mistakes to avoid

Practise Astrophysics — free games

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