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I am curious about making the inner walls of this blackbody perfectly reflecting instead of perfectly absorbing.

  1. If I keep on giving in incident radiation,the photon density inside will increase, will it result in any interesting observation?

  2. There will still be a non-zero radiation escaping out through the inlet,so after giving in a large amount of radiation,will it work like a torch, with radiation escaping the closed system over time?

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Q1: If light can come in through the opening, it can also come out through it. So it isn't possible to concentrate energy inside arbitrarily. Reflecting walls means the outgoing radiation spectrum will be similar to incoming radiation, it won't be changed much by thermalization. But the outgoing radiation will have large beam spread - if light is coming in as thin beam, it won't be coming out as such, but will go out in all possible directions.

Q2: Yes, but this is all very quick, so there won't be observable delay. As soon as light is coming in, outgoing light is also going out.

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