## Example 1.3 in the textbook

(Wien's law: )

Leslie Contreras 1D
Posts: 35
Joined: Fri Apr 06, 2018 11:02 am

### Example 1.3 in the textbook

We were only shown Weins law but will we use Stefan-Boltzmann
law Total intensity=constant xT^4
When will this concept come up? Can someone explain to me why T^4

Posts: 30
Joined: Fri Apr 06, 2018 11:01 am

### Re: Example 1.3 in the textbook

I think there will be some concept based questions on stefan boltzmann law, at the very least.

For the second part of your question, T^4 because it was found that the intensity is not simply directly proportional to T, but it is proportional to T^4 (the temperature to the 4th power). The unit used for temperature in the stefan boltzmann law is generally the Kelvin.

Steve H
Posts: 8
Joined: Fri Apr 06, 2018 11:03 am

### Re: Example 1.3 in the textbook

An example question: What equation helps astronomers determine a star's temperature, size, composition, and age of a star? Because this concept is new to us and very complex, I am sure there will not be many questions about this on the final/midterm.

Chem_Mod
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### Re: Example 1.3 in the textbook

There is a physical reason why it should be T^4 which becomes apparent as you start deriving it. However, I will not explain it here since you need to understand statistical mechanics, which you start encountering in upper division physics courses.