So if you have a light bulb in a room, and you had a tool to measure the amount of light that's in the room, then let's assume the amount of light only caused by the bulb is "1"
If you place a mirror next to the bulb, does the amount of light in the room in crease to "2"?
Can you keep going so that the light in the room in creases to 3..etc with more mirrors?
How far can you take this? Also, is it actually adding light to the room, or is it simply causing the same photons to move faster (reflecting from one mirror to the next) making it seem like there is more light in the room, but there really isn't?
Made me think, so I thought I ask here 🙂
Best Answer
I think that the other two answers miss an interesting point of your question. Lets put a light bulb inside 100% reflecting sphere. All emitted photons will stay inside the sphere and intensity of light will continuously increase to infinity.
Real mirrors are never 100% reflective but there are mirrors with 99.98 reflectivity (these are dichroic mirrors that work only in a narrow wavelength range). With such mirrors light can reflect 1000 times before escaping the sphere so light intensity inside the sphere will be 1000 times higher compared to a lamp without mirrors. The energy conservation is not violated because new photons are not created.
What we just created is actually an optical resonator although normally we have a one-dimensional case with two parallel mirrors and a laser pulse trapped between them (as in Cavity ring-down spectroscopy). Concave mirrors are used for better light trapping.