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# Note for Applied Physics - Phy By vtu rangers

• Applied Physics - Phy
• Note
• Visvesvaraya Technological University Regional Center - VTU
• 17 Topics
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#### Text from page-2

LAWS GOVERNING THE BLACKBODY RADIATION: 1. Wien’s Law 2. Wien’s Displacement Law 3. Stefan’s Law 4. Rayleigh-Jeans Law 5. Kirchoff’s Law 6. Planck’s Law WIEN’S LAW: Wien’s law gives the relation between the wavelength of emitted radiation and the temperature of the source as, E d  C15 e C2 T d Where C1 and C2 are constants and E  d is the energy emitted per unit volume in the wavelength region  and +d. This law is called Wien’s law of energy distribution in the blackbody radiation spectrum. Drawbacks of wien’s law: Wien’s law holds good only for shorter values of wavelength but fails to explain the region in which wavelengths are longer. RAYLEIGH-JEANS LAW: In 1900, Lord Rayleigh applied the principle of equipartition of energy to electromagnetic vibrations and deduced an equation for the black body raidiation. This was later modified by Sir James Jeans and came to be called Rayleigh-Jeans law. According to this law the energy density i.e. the amount of energy per unit volume of a blackbody in the wavelength ranging from  to +d is given by E d  8kT4 d Where, k is Boltzmann constant. Due to the presence of the factor λ-4 in the equation, the energy radiated by the blackbody should rapidly decrease with the increase in wavelength. Drawbacks of Rayleigh-Jeans law (or Ultraviolet catastrophe): Rayleigh-Jeans law holds good for longer values of wavelength but does not fit the experimental curves for shorter values of wavelength. Department of Physics Page 2