Asked by: Jenny McGrath, Dublin

Advertisement

Old-fashioned television sets and computer monitors rely on a cathode ray gun to shoot electrons at a phosphor screen. But the electrons are only released when the cathode emitter is heated, hence the few seconds needed for the set to warm up.

Plasma and LCD devices, on the other hand, emit light pretty much instantaneously when the power is switched on.


Advertisement

Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.

Advertisement
Advertisement
Advertisement