# Blackbody Radiation

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Name ___Katie Hastings___ Blackbody Radiation Lab 11 Go to http://phet.colorado.edu/simulations/sims.php?sim=Blackbody_Spectrum and click on Run Now.

1) In this lab, you will use the Blackbody Spectrum Simulation to investigate how the spectrum of electromagnetic radiation emitted by objects is affected by the object's temperature. In this simulation, you can input the temperature and observe the spectrum of the radiation emitted. a) The temperature of stars in the universe varies with the type of star and the age of the star among other things. By looking at the shape of the spectrum of light emitted by a star, we can tell something about its average surface temperature. i) If we observe a star's spectrum and find that the peak power occurs at the border between red and infrared light, what is the approximate surface temperature of the star? (in degrees C) -The surface temperature of the star is 4040 K. This temperature converted into degrees C is equal to 3767 C. ii) If we observe a stars spectrum and find that the peak power occurs at the border between blue and ultraviolet light, what is the surface temperature of the star? (in degrees C) -In this case, the surface temperature would be 7100 K. This temperature would equal 6827 C.

b) Light bulbs operate at 2500 degrees C.
i) What is the wavelength at which the most power is emitted for a light bulb operating at 2500 C? -2500 C to Kelvin = 2773 K, peak power = 1050 nm
ii) Explain why regular incandescent bulbs waste a lot of energy. Be sure to include your reasoning. - Less than 15% of energy is used to produce visible light. With that being said, most of the light emitted in part i) of the simulation, is at wavelengths longer than the visible. So, all the energy used to produce light that is not at visible wavelengths is wasted. This is why incandescent bulbs waste energy.

2) In this problem we will...