Can you provide more information? I'm not sure what you have to do.

Meanwhile, I can give you a few bits and pieces that might prove useful. Consider a photon propagating at c. We say it's massless. As it happens, it has a non-zero "active gravitational mass" and a non-zero "inertial mass", but when we say mass without qualification, we usually mean rest mass. And the photon has no rest mass because it's never at rest.

However there is a trick, where you catch the photon in a gedanken mirror-box. The photon isn't actually at rest, but it's bouncing back and forth so it's

*effectively* at rest. And it increases the mass of the system. The inertia of the box-system is increased. The box is harder to move because the photon is in there. Then when you open the box it's a radiating body that loses mass, just like Einstein's

E=mc² paper. (As an aside, look at the last line: *"If the theory corresponds to the facts, radiation conveys inertia between the emitting and absorbing bodies".* That's why the photon has a non-zero inertial mass. Which is actually a measure of energy.)
Now here's the important thing: If the photon is moving at c, none of its energy-momentum is exhibited as mass. If the photon is effectively moving at a speed of zero, all of its energy-momentum is exhibited as mass.

*And there's a sliding scale in between*. If you slow the photon down a little, some of its energy-momentum is exhibited as "effective mass".

(Google it). So if your photon enters a glass block, it slows down a little and the mass of the glass block increases a little. So the photon is behaving a little like a massive boson. See

this though. And note that you have to do the work for yourself. If you get too much help, that's not good. But ask around anyway. Ah, I see

Kyle Kanos was a bit curt!