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Blackbody Radiation Question 5: Comparing Planck's Law for Different Stars

Sirius is known as the blue star because its spectrum of light emitted is shifted to the higher frequencies, while Betelgeuse is the red star because it emits mainly lower frequency light.

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In this video I compare the blackbody radiation of different stars by graphing out Planck's Law for the Sun, Sirius, Procyon, and Betelgeuse stars. Sirius is known as the blue star because most of its energy density is from high energy blue light. Betelgeuse is known as the red star because it emits mainly low energy red light. The spectrum of Procyon is similar to that of our Sun but it's energy density is magnified for each frequency or wavelength of light emitted.

Timestamps:

  • Question 5: Graph Planck's Law for Betelgeuse, Procyon, Sirius, Sun: 0:00

  • Solution: Graphing Planck's Law for different temperature stars: 0:41

  • Zoomed in look at Betelgeuse and the Sun: 2:18

  • As temperature increases, the total area under the curve increases (more energy it emits): 2:43

  • As temperature increases, the wavelength at maximum energy density decreases: 3:22

  • Sirius is a blue star because it emits high energy short wavelength light. Betelgeuse is a red star because it emits low energy high wavelength light: 3:52

  • Electromagnetic and Visible light spectrum (0.39 to 0.76 um): 4:10

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