What is Light? When we talk about light we refer to the narrow...
3 Oct 2011, 20:13 UTC
What is Light?
When we talk about light we refer to the narrow band of electromagnetic spectrum that is visible to the human eye. So the range of visible light corresponds to wavelengths from 380 nanometers to 740 nm.
As you can see in the picture, we say that’s a narrow band for a reason, it’s very limited! All we can see in the universe with our eyes is in fact in that small band of the electromagnetic spectrum, the colors from violet to red. There’s an infinite numbers of other “colors” that we can “see” only through some appropriate instrument.
Here’s for example two different views of the same nebula, in visible light on the left and in infrared on the right:
Now, when we have spoken about the wavelength of light, we have implicitly assumed that the light is a wave, but as Einstein showed with his photoelectric effect in 1905 light is made of particles he called light quanta, what we now call photons.
But now wait, is light a wave or is it made of particles, it can’t be both! Turns out it can. This very strange behavior of light, one of the most counter-intuitive concept ...
