@Devin-M, allow me to pose a question. If you understand the question and its answer I think it might clear up some confusion. So I won't give you the answer in this particular post. I want you to think about it.
Does the size of a constant-temperature, empty box, or a box with only solid objects (at same temperature), change the average photon power flux within the box? What, if anything, can you do to change the photon power flux within the box?
You have an HgCdTe IR photodetector of a fixed makeup (fixed size, color, material, etc). You also have a closed box, with black (opaque) inside surfaces, in which the detector can fit. You put the detector in the box. The box is always at 300 K. When you put the detector in the box, the detector is also at 300 K. For simplicity, let's assume that at this point, besides the detector, the rest of box contains vacuum (this vacuum part is only important because I don't want to get into more complicated gas laws and phase transitions and whatnot: the box can contain solid objects and that's it. The rest of the volume is vacuum).
Your goal: increase the photon power flux (photon energy per unit time, per unit area of the detector's surface) hitting the surface of the detector. Essentially, you're just trying to increase the rate that photons strike the detector.
Things you are not allowed to change:
- You cannot insert any form of energy into or out of the box. There are no holes in the box (besides a special-purpose airlock discussed below). That means no electrical wires coming into or out of the box. You cannot use electromagnetic fields to transfer energy into our out of the box. No radioactive energy transfer is allowed either. Gravitational waves are also not allowed.
- You cannot change the temperature of the box. The box, must at all times, remain exactly at 300 K. It's assumed that you can easily keep the box at a constant 300 K.
- You cannot change the size and shape of the detector. It must stay in its original form.
- You cannot manipulate the temperature of anything in the box after it is put it in the box.
- You cannot change the outside surface material/color/etc. of the box. The box must always remain opaque.
- You cannot put two separate items into the box that chemically react with each other. That would violate the "stored energy" rule (see blow).
- Same thing with radioactive material. Stuffing the box with 235U until it reaches critical mass is right out.
- You cannot shake up the box. (You can't jostle it back and forth, or strike it with hammers, or anything that would cause its contents to heat up through friction.) That includes spinning the box like a clothes dryer tumbler. That's not allowed.
Things you can change:
- You are allowed to slowly change the size of the box (slow enough not to excessively jostle the contents). The box must be big enough not to compress the detector or anything else in the box. But you can change its size. You can increase it to the size of a large city if you wish, or just small enough to hold its contents without squishing them. Or anything in between. The box is ideal in that if you change the size of the box, you don't need to worry about its surface temperature changing. This special box will always keep its properties (temperature, color, etc), even if you change its size.
- You can add (through an airlock) other solid objects into the box (e.g., marbles, dice, other photodetectors, kitchenware, statues, bridges, castles, lenses, mirrors, etc.) so long as (a) they are also at 300 K, and (b) they do not contain any stored energy and (c) they do not sublimate into gaseous form. (For example, you cannot add a battery or cheese, or a match, or a moose, or antimatter. You cannot add highly compressed, solidified nitrogen or any highly compressed gas [for two reasons, one because there is stored energy, and another because it could become gaseous].) The solid items must remain in their original, solid form. Also, the items must fit inside the box; it's OK to increase the size of the box before you put them in though, so they'll fit.
- You can slowly move items around within the box (slow enough not to cause friction/frictional heating though). In other words, you are allowed to move items closer to or farther away from the detector.
So what, if anything, can you do to increase the average photon power flux hitting the detector? Explain your answer.
Bonus question: how does this compare to the photon power flux leaving (emitted by) the surface of the detector?