Question

why can you see an electric bulb at night when it is switched on

Answer 1

When we see in a completely dark room, we see nothing as there is any light in the dark room.
(a) If we switch on an electric bulb in this dark room as a light source we can see bulb due to the light emitted by it.
(b) If we switch on an electric bulb in this dark room as a light source we can see a piece of white paper as it reflects the light from the bulb falling on it.

Answer 2

Answer:

It is because it is a source of light and we can see it because it reflects light to our eyes.