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Black-body radiationEdexcel A-Level Physics: Flashcards

What these 12 flashcards ask

  • What is a black body?
  • Describe the shape of a black-body radiation curve.
  • How does the peak wavelength change as temperature increases?
  • How does intensity at a given wavelength change as temperature increases?
  • State the Stefan-Boltzmann law.
  • Give the value of the Stefan-Boltzmann constant.
  • What is the surface area of a spherical star?
  • State Wien's law.
  • The temperature of a star doubles at constant radius. How does its luminosity change?
  • Why does a star at 3000 K look red?
  • Write the ratio L₁/L₂ for two stars in terms of radius and temperature.
  • Why can a cool star be very luminous?

Exam questions on Black-body radiation

  1. The interior of a furnace is held at a constant temperature of 1500 K. Engineers model the furnace interior as a black-body radiator.
    The temperature of the furnace interior is raised to 1800 K. State and explain two ways in which the radiation curve of the furnace changes.2 marks
  2. A star has a constant radius while its surface temperature rises from 5000 K to 10 000 K. Treat the star as a black body.
    Explain why the star appears bluer when its surface temperature is 10 000 K than when it is 5000 K.2 marks
  3. The Sun radiates approximately as a black body. The wavelength at which it emits radiation most intensely is 5.0 × 10⁻⁷ m, and its radius is 7.0 × 10⁸ m.
    Calculate the surface temperature of the Sun.3 marks
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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).