1. The light from the candle travels straight in all directions from each point of the flame of the candle.
2. But only the light coming in some particular directions can enter into the camera through its pin-hole.
3. The light that comes from the point at the top of the flame goes straight towards the bottom of the screen.
4. And the light that comes from the point at the bottom of the flame goes straight towards the top of the screen.
5. In this way, the light coming in a particular direction from each point of the flame will be able to enter into the pin-hole.
6. And light going in other directions is blocked by the black sheet.
7. This leads to the formation of an inverted image.
8. The formation of an inverted image on the screen of the pinhole camera explains that light travels in a straight line.
