UV Catastrophe and Black-Body Radiation

• What is a perfect black body defined as?

  A theoretical object absorbing all radiation
• Why is a perfect black body considered the best emitter?

  Because a good absorber is also a good emitter
• What is the spectrum of electromagnetic radiation emitted by a black body called?

  Black-body spectrum

  
• How does the black-body spectrum change?

  It changes depending on the temperature
• What does a cube of metal at room temperature emit?

  Invisible infrared radiation
• What happens to a metal cube when heated to 3000 K?

  It emits visible light and glows
• What does the graph of black-body radiation show?

  • Each curve represents the same black-body at different temperatures
  • The peak indicates the wavelength of maximum intensity
  • Cooler objects emit in the infrared range
  • Higher temperatures emit shorter wavelengths

  
• What was the Ultra-Violet Catastrophe?

  A disagreement between experimental and predicted spectra
• What did classical physics predict about black-body radiation?

  It predicted infinite ultra-violet emission
• What was the significance of the discrepancy in black-body radiation theories?

  • Indicated that classical physics was incorrect
  • Required adaptation or replacement of the theory
  • Highlighted the need for new scientific approaches
• Who addressed the problem of the Ultra-Violet Catastrophe?

  Max Planck
• What did Planck propose about energy emission?

  Energy is quantised in integer multiples
• How is the energy emitted by an oscillator of frequency f expressed mathematically?

  E = nhf
• What does 'h' represent in the equation E = nhf?

  Planck's constant
• What is the value of Planck's constant?

  6.63 × 10^-34 J s
• How did Planck's theory explain black-body spectra?

  • Mathematically described emission and absorption
  • Fit experimental data accurately
  • Introduced the concept of quantised energy
• How can understanding quantisation aid in learning about electrons?

  • Revisiting quantisation in different contexts
  • Helps clarify the concept of energy packets
  • Connects to the charge of an electron