Eli5 why doesn’t the light from a lightbulb make the room brighter over time if the lightbulb keeps emitting photons?

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When I turn the light on in my room, it emits photons. Is it a continuous stream of photons travelling at the speed of light? Why can’t there be ‘too much light’?

Let’s say i imagine the lightbulb is a garden hose with water coming out (photons). Why doesn’t the lit up surface the photons reflect off of get wet (saturated)?

When I look at a wall in a lit up room, do those photons travel to my eyes?

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3 Answers

Anonymous 0 Comments

For the same reason that when you turn off the lightbulb, it gets dark:

The light is absorbed.

Let’s say that the walls reflect 90% of the light (very reflective!), and let’s say the lightbulb emits 10000000000000000000 photons per second, and that the room is a sphere of radius 1 m. A photon would hit the wall every 0.000000001 seconds, and would have a 10% chance of getting absorbed. After every 0.000000001 seconds there would be 10% less light. After every 0.000000007 seconds there would be only half the light. After just 0.0000004 seconds the photons will pretty much be 100% absorbed.

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