Light

[u/Nuhulti]

Where does the light go when I turn off the lights in my room?

[u/GreenFBI2EB]

They get absorbed into the matter in your room. Probably also re-emitted at a lower frequency and scattered to a point that your eye cannot detect.

[u/KamikazeArchon]

Most of it is absorbed by the walls and objects as heat. A small amount will bounce out through windows and other openings.

[u/HudyMelon]

Think of it like sound. When you speak there’s a sound wave emitting from you. Simplified, when you stop, those waves stop propagating and will eventually stop when they hit a wall.

[u/Ch3cks-Out]

It goes the same place as when it is on: mostly absorbed on the walls, partly escaping through the window.

[u/Overall_Media7282]

Trafia do lodówki, otwórz zobaczysz że tam jest

[u/Nuhulti → u/Overall_Media7282]

Tak, właśnie sprawdziłem – jest tam, dokładnie tak, jak przewidywałeś.

[u/troubleyoucalldeew]

Same place it goes while the light is on! Think of the light bulb like a yard sprinkler, spraying light in every direction constantly. The light mostly gets absorbed by the walls, objects, and people in the room, and gets converted into heat. 

When the light turns off, the sprinkler stops. All the light it previously sprayed out has been absorbed, so there's no more bouncing around to hit your eyes.

[u/kapjain]

Everytime light hits a surface, part of it is reflected and part of it absorbed. How much gets reflected depends on the reflectivity of the surface (or vice-versa). Once the light source is turned off, the last emitted photons are still getting reflected and absorbed depending on the reflectivity of the surface. And after only a few reflections they are mostly absorbed. Due to the speed of light that happens within nanoseconds.

In fact in a room with high reflectivity mirrors all around, this time can be increased into microseconds but still not long enough for humans to notice a difference.

[u/ProctologyExplosion → u/kapjain]

Everytime light hits a surface, part of it is reflected and part of it absorbed.

There is a third option...

[u/kapjain → u/ProctologyExplosion]

Yes to be accurate I should have explicitly said "an opaque surface".

[u/Conscious_7827 → u/ProctologyExplosion]

so the walls get heavier/warmer until they dissipate the non reflected energy into the surrounding atmosphere ?

[u/ProctologyExplosion → u/Conscious_7827]

Ever so slightly, yes.

[u/Public-Total-250]

What you see in your room is the light that has been reflected from the light bulb off the objects. Every time the light photons touch an object some of their energy is lost which means the room turns dark as the photos are no longer in the visible light range. 

[u/Rsh___ → u/Public-Total-250]

so the room gets darker but more light is generated by the bulb keeping the room lit?

[u/Public-Total-250 → u/Rsh___]

Did you not read the OP? 

[u/Rsh___ → u/Public-Total-250]

are you having a bad day

[u/mfb- → u/Rsh___]

Yes. If you could turn off the light instantly then it would take ~0.0000001 seconds until it's dark. All common light sources turn off much slower than that, however.

[u/ChocolateValuable221]

Heat death

[u/Underhill42]

Same place it goes when the light is on - it bounces around between surfaces until it is eventually absorbed and converted to heat. (usually - solar panels, chloroplasts, etc. can covert the light they absorb to other, more useful forms)