# Homework Help: Plank's law

1. Nov 3, 2007

### vahide

could you find the planks formulas transformation for high and low frequencies please.

2. Nov 3, 2007

### cristo

Staff Emeritus
Last edited by a moderator: May 3, 2017
3. Nov 3, 2007

### vahide

planks law

could you declare the planks formula through $$\lambda$$ please

4. Nov 3, 2007

### vahide

Last edited by a moderator: May 3, 2017
5. Nov 3, 2007

### cristo

Staff Emeritus
You'll have to help me help you. Is the link I provided for you any use? If so, you (should) know a formula relating frequency and wavelength.

6. Nov 3, 2007

### cristo

Staff Emeritus
There's a proof on that page!

7. Nov 3, 2007

### vahide

planks law

could you prove this
$$\lambda_{max}$$*T=constant=x
and find x
by planks formula?

8. Nov 4, 2007

### malawi_glenn

yes, that is Wiens displacement law.
Just Do the "approximation" Wien "did" and find maximum. I.e remove the (-1) in the denominator in placks law.

Wiens radiation law is for small wavelengths, and Rayleighs is for large. Planck is for all.
Now try figure out WHY the (-1) is removed in order to get Wiens law from placks law.