Luminosity and intensity of starsEdexcel A-Level Physics: Mind map

Exam questions on Luminosity and intensity of stars

1. An astronomer measures the intensity of the light received from distant stars using a telescope fitted with a sensitive detector.
   Explain why the intensity of the light received from a star decreases as the distance from the star increases.2 marks
2. The Sun has a luminosity of 3.85 × 10²⁶ W. The mean distance from the Sun to the Earth is 1.5 × 10¹¹ m. Assume that the Sun radiates equally in all directions and that no radiation is absorbed on its way to the planets.
   The planet Mars is 2.3 × 10¹¹ m from the Sun. Calculate the intensity of sunlight at Mars.2 marks
3. Astronomers measure the intensity of light from a bright star, S, as 1.2 × 10⁻⁷ W m⁻² at the Earth. Star S is 8.1 × 10¹⁶ m from the Earth.
   Calculate the luminosity of star S.3 marks