Question

Why is lightning seen at once, but the clap of thunder heard after some time?

Answer 1

Here is your ans-
It is because light travels faster than sound.So we see the lightning first then hear the thunder.
You can also do an experiment to know it. you stand at a distance from where you can see a car but it is quite far.Then tell someone to shut the door of the car.You will first watch the door closed and then hear the shutting sound.
 Hope it helps.

Answer 2

We know that light travels faster than sound.
This is why we see the lightning first, and then hear the thunder

One more example: When we see a cricket match in a stadium, we will first see the ball coming in contact with the bat and then we will hear the sound of the cricket bat hitting the ball.

Cheers!!