Discover - How Various Objects Give Off Light


Both the Sun and a television are sources of light, but are they the same? You know one is a natural source and one is artificial. However, is there any other difference? Can a plant use both sources to make food? Can YOU use both sources of light the same way?

Clearly different light sources will perform different functions, and usually this is related to differences in brightness or luminescence.



The bright light you might want in your fridge to see your food...




...will be different that the dim light you use in your bedroom for a nightlight.




Some things look like they give off light, but they are not actually sources of light.  Mirrors or reflectors on bicycles might look as if they are glowing or shining light, but they are just reflecting the light from other sources.

Watch the following video to learn more about various objects that give off light.  Think about whether each object is actually a source of light and how the amount of luminescence makes it useful.

Question: How do various things give off light?


Video

Sources of Light Video

Science Connection

Likely, you have seen a cat at night. Its eyes seem to glow when a light shines on them.  Are cat's eyes a source of light? Actually, cats and some other animals have a special layer in their eye called a tapetum that reflects light to help them see better in the dark. The glowing you see is just the tapetum reflecting light back to you.

Learn more about why animal's eyes glow.