# Physics

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’s surface is not affected by the concentration of greenhouse gases in the atmosphere.

True or False

At higher temperatures, the Earth’s surface emits more IR radiation.

True or False

During the ice age, the amount of sunlight absorbed by the Earth’s surface decreased.

True or False

All greenhouse gases are from anthropogenic sources (that is due to man’s activities).

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