- #1

Edward258

- 1

- 0

## Homework Statement

It's a Blackbody radiation problem:

A beam of wavelength λ, in the state of right circular polarization, leads to an absorbent disk.The mass of the disk is m, it's specific heat is C, and its moment of inertia is I .The disk is initially at rest, but after a lapse of time has an angular velocity Ω. Show that the temperature increases in:

ΔT=(IΩ/mC)(2πc/λ-Ω/2)

## Homework Equations

Q=CmΔT

## The Attempt at a Solution

From the equation;

Q=CmΔT

I can get ΔT

ΔT=Q/Cm

And

Q=U2-U1

So

ΔT=(U2-U1)/Cm

But I don't know how to justify that;

U1=IΩ

^{2}/2 ------- Rotational kinetic energy

U2=(IΩ2πc)/λ --------- con E=hc/λ Photon energy