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# Review. The cosmic background radiation is blackbody radiation from a source at a temperature of 2.73 $\mathrm{K}$ . (a) Use Wien's law to determine the wavelength at which this radiation has its maximum intensity. (b) In what part of the electromagnetic spectrum is the peak of the distribution?

## 1.0165 $\mathrm{mm}$

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##### Andy C.

University of Michigan - Ann Arbor

##### Marshall S.

University of Washington

### Video Transcript

vines Law states that Lambda Max Max leg length times temperature is equal to a constant and that constant being two point 898 um, times 10 to the negative. Three, um, meters times Calvin Um, And so Lambda Max, therefore, is just, uh, this value over the temperature of the cosmic microwave background, which is 2.73 Calvin is what it's observed to be, uh, and so maximum wavelength is 1.6 times 10 to the negative three meters. So this is 1.6 millimeters, Uh, and so, um millimeters are in. So we know that, uh, so this is obviously a higher way blank lower energy region. So it's ah, it's past the visible. Even past the infrared is actually a microwave on DSO. As the name implies, this is microwave radiation at one just over one millimeters

New Mexico State University
##### Andy C.

University of Michigan - Ann Arbor

##### Marshall S.

University of Washington