Wien's forskyvnings lov

• Forging metal


  1. Blacksmith puts steel rod in flame

  2. Blacksmith judges how hot the metal rod is by watching the changing colour of the steel
• In chemistry lessons, you would have used Bunsen burners and noticed that you can get a blue flame from it whereas a tea candle burns with a yellowish flame
• As an object gets hotter

  • It begins to emit more light at every wavelength so that it gets brighter
  • The peak of the emission shifts to the blue end of the spectrum
• Wavelength


  1. axis on a graph
• Intensity of the wave

  1. axis on a graph
• Star with surface temperature of 4000 Kelvin


  • Emits radiation with all wavelengths ranging from infrared to visible light to ultraviolet
  • Peak intensity is around 700 nm in the red region of the visible light spectrum
• Star with surface temperature of 7000 Kelvin


  • Emits all wavelengths at a higher intensity
  • Peak has shifted towards the left hand side so that the maximum intensity is now in the blue region
• Object's temperature


  Inversely proportional to peak wavelength
• Wien's displacement law


  The peak wavelength is inversely proportional to temperature, with a constant of proportionality called the Wien's constant (2.898 x 10^-3 meters Kelvin)
• Black body


  • An object that absorbs all radiation incident upon it and then re-radiates all energy
• The Sun can be approximated as a black body that has a surface temperature of 5800 Kelvin
• The Sun emits the most visible light in the green region
• Our eyes have receptors for red, green, and blue colours
• Our brain mixes all three colours together forming white