In this video Dr. Carlson demonstrates the properties of light. Light is like a wave and it is also like a particle, which means that it comes in small packets. To demonstrate how we know that light behaves like packets of energy, he uses LED‚Äôs in different colors and a sheet of phosphorescent paper. When light with a high enough energy shines on the paper it will cause the paper to glow.
Light comes in many different colors, this is known as the electromagnetic spectrum. Red is low energy light and purple is high energy. When the red light shines on the paper it doesn‚Äôt glow; the same happens with the orange, yellow and green. However, blue and purple do have enough energy to cause the paper to glow.
The demonstration proves that all colors below blue do not have high enough energy to activate the paper, even in large quantities, so by this we know that light comes in particle form, in other words photons.