IB · E · multiple choice
Nuclear and quantum physics · Question 5
Nuclear and quantum physics · Original GioPhysics question with a detailed, mark-by-mark answer guide.
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multiple choice1 mark
Two stars have the same surface temperature, but star P has four times the radius of star Q. What is the ratio of their luminosities, L_P : L_Q?
- A
4 : 1
- B
8 : 1
- C
16 : 1
- D
256 : 1
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Answer overviewCorrect answer: C — 16 : 1
01
1 markAnswer and reasoning
How to approach it
Predict from the governing principle before looking for a matching option. Then reject alternatives by checking direction, units, limiting behaviour or the physical meaning of each statement.
- 1
The correct choice is C: 16 : 1
- 2
D applies the fourth power to the radius instead of to the temperature. Luminosity is 4πR²σT⁴ — the radius enters squared, the temperature to the fourth.
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