Black-body radiation and stellar luminosityEdexcel International A Level Physics: Mind map

Exam questions on Black-body radiation and stellar luminosity

1. A star of radius 6.96 × 10⁸ m has a surface temperature of 5.80 × 10³ K and may be treated as a black body radiator. A planet orbits it at a distance of 1.50 × 10¹¹ m. Use: Stefan–Boltzmann constant σ = 5.67 × 10⁻⁸ W m⁻² K⁻⁴; Wien's law constant = 2.898 × 10⁻³ m K.
   Calculate the intensity of the radiation from the star at the planet.2 marks
2. Two stars, A and B, have the same radius and may both be treated as black body radiators. The surface temperature of star A is 3500 K and that of star B is 7000 K. Use: Stefan–Boltzmann constant σ = 5.67 × 10⁻⁸ W m⁻² K⁻⁴; Wien's law constant = 2.898 × 10⁻³ m K.
   Explain why star B appears bluer than star A.2 marks
3. An astronomer studies a star that radiates as a black body with a luminosity of 2.5 × 10²⁸ W. The star is at a distance of 8.1 × 10¹⁶ m from the Earth. The wavelength at which the radiation from the star has maximum intensity is 293 nm. Use: Stefan–Boltzmann constant σ = 5.67 × 10⁻⁸ W m⁻² K⁻⁴; Wien's law constant = 2.898 × 10⁻³ m K.
   Calculate the intensity of the radiation from the star at the Earth.3 marks