[kesavan]

How clock’s needles transmit light at night?

[tickle]

Fluorescent paint

[Capuchin]

Sorry tickle I hated giving you a disagree.

Fluorescent materials are used in fluorescent tubes, they emit a low wavelength light when a higher wavelength light is incident on it. The timescale for this reaction is on the order of nanoseconds. This is useful because you don't want your fluorescent tube emitting light after you have turned it off.

Glow-in-the-dark objects like clock hands use phosphorescent materials. Most of these materials re-emit the light they absorb some milliseconds after the initial excitation, but if you choose the phosphorescent material carefully the light can be held in the material for some hours before re-emission, which gives the glow-in-the-dark effect. This is why you have to recharge these materials if they have been in the dark for a long time.

The other readily used way to get things to glow in the dark is chemiluminescence. This is apparent in glow-sticks where you have to bend the chamber to get two substances to mix, which then produce light.

[tickle]

Oh heck capuchin, I should have known that!

[asterisk_man]

My grandfather had (has?) a watch that uses Radioluminescence to make the hands glow.