Light is often identified by its source (a light bulb, a candle, the Sun …), or by its effect on an object that diffuses it (the Moon, an illuminated page…). In fact, light is invisible radiation unless it actually penetrates our eyes.
When we think we are seeing a beam of light, it is actually dust or other particles which are acting as a screen, reflecting the light to our eyes. Thus, in fact, it is the dust, not the light, that we are actually seeing.

Use the buttons at upper right to switch between clear air and dusty air.
Then click and drag the magnifier over the box.