If I flick the light switch on and off will it damage the light?
Incandescent filament lamps resistance changes dramatically - up to ten times - as they warm up. The result is that there is a large inrush current initially but as the element heats the resistance increases and the current decreases to its nominal value. This explains why bulbs generally popped on switch-on rather than at a random moment when burning steadily. (The thermal inertia of the element is high enough that it doesn't cool down between AC mains half-cycles.)

During rapid switching the filament would not cool completely before the next switch-on so it would not be stressed so much. The longer the 'off' periods the harder it is for the lamp.

My domestic experience was that lamps on dimmer switches lasted 'forever' relative to the other lamps in the house. This was due to the rotary dimmer being turned up over, say, half a second and gradually increasing the current while the element warmed up. There was no sudden inrush current.

Lamptech have an article on the subject with some graphs and response times. They also contradict me regarding longer off times. (Ah well.)