Get a piece of card and cut some narrow slits in it, as though you were making a comb. The diagram on the main screen shows you what it should look like.

Then place the card upright in a dark room and shine a torch beam through the card.

What do you notice?

The card blocks some of the light beam and you see a pattern of narrow beams instead.

Can you see how all of the light beams are straight lines?

Light always travels in straight lines, so you cannot make light go around corners.