Name __________________ Blackbody Radiation Lab 11 Go to http://phet.colorado.ed
ID: 1268926 • Letter: N
Question
Name __________________ 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)
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)
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?
ii) Explain why regular incandescent bulbs waste a lot of energy. Be sure to include your reasoning.
2) In this problem we will explore the greenhouse effect by using the Greenhouse Effect Simulation available from http://phet.colorado.edu/simulations/sims.php?sim=The_Greenhouse_Effect
a)Explore the simulation.
True or False
The only effect of increasing the number of clouds is to reduce the amount of sunlight absorbed by the surface of the earth.
True or False
Increasing the concentration of greenhouse gases, increases the amount of radiation that Earth emits to space.
True or False
When sunlight encounters a cloud, the cloud reflects about 10% of the sunlight back to space.
True or False
When there is a very large concentration of greenhouse gases, most of the IR radiation reaching space has interacted with greenhouse gas molecules on its way from the surface to space.
True or False
The total amount of radiation absorbed by the Earth
Explanation / Answer
One simulation at a time please.........
a) i) The peak power is between red and infrared region at around 4035 Kelvins. Therefore, surface temperature of star is 4035 - 273 = 3762 oC.
ii) For peak power between blue and UV, the temperature is around 7100 K, so surface temperature is given as
7100 - 273 = 6827 oC
b) i) Temperature of bulb in Kelvin = 2500 + 273 = 2773 K,
for this temperature, the wavelength value is approximately 1.03 micrometers (um) or 1030 nanometers (nm)
ii) Most of the energy is emitted at wavelengths beyond the visible region. It means that most of the energy is utilized in production of light not illumniating the objects, it means this energy is getting wasted.
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