 We are speaking to our good old friend Albert Einstein. He's just about to tell us about the properties of light. "As I was saying in the previous section, light is a wave, but it sometimes acts as a stream of matter. Anyway, with experiments from playing with mirrors you might have figured out that light reflects off a reflective surface. An interesting characteristic of light is that the angle from the plane where you shoot a beam of light, is equal to the angle of reflection for the reflected beam. This is why objects in a flat mirror appear to be at the same depth behind a mirror. After all, all objects are seen because light is reflected from them to our eyes." "Very angular Albert. Now you said that light acted like a wave. What interesting characteristics do you have to tell us that support that?" "Well you see, waves have a neat characteristic when they pass through a small opening. They diffract: meaning they interfere with each other and move outwards in a circular pattern from the opening. You can do a neat little experiment to test this by taking your two index fingers and putting them really close together. Place them so close that when you look at a bright object, you can see black lines in the small gap. Those black lines are created by interference from the waves. Here, the waves essentially cancel themselves out, and you are left with an absence of light - black." "Wow, that's pretty neat." We will speak to Albert again in a few short seconds, but as usual when we encounter a new topic, we have to click to proceed. So do the later!" 
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Light is a
wave, but sometimes acts as if it were a stream of particles