Why do CFL's take about half a second to turn on, but normal bulbs are instant-on?

Question

Every single CFL that I own that is 15watts or under is not instant-on. The package claims that it is instant-on, but it is not. Why is this?

I own two 20watt bulbs, and one of them is instant-on. I'm really puzzled because I thought that if one of the 20watts was instant-on, then the both should be. Most of my bulbs are the same brand (GE), but three bulbs are from Sylvania.

Please explain!!! Thanks.

Answer 1

Most of the new CFL's are almost instant on.

They work by emmission of free electrons which colide with mercury molecules that in turn emit ultra-violet photons.

The ultra-violet photons colide with the fluorescent powder which coats the inside of the tube. When this collision occurrs, visible light is emmitted.

It takes a very small amount for this process to start.

Incadescent bulbs on the other hand have a filament which heats to white hot and emmits visible light. This takes much less time than the CFL.

The trade off is less cost with CFL's and less heat produced. Incadence bulbs use over 60% of the electricity to produce heat.

Good Luck.

Answer 2

Basically, it needs to warm up, ad the others turn on at the speed of light.