 In this section we will start off by answering the age old question, "What is light?" Now as you might have figured out from our adventures in the other sections, I need the help of some people to get the idea across. For this section we will talk to my best friend and yours, Albert Einstein. There's big Al right now. "Hello Albert, can I ask you some more questions please?" "Of course you may, your wonderful hat has reminded me of home!" "Thank you Albert. You know I do have some more at home. I could sell you some at a cheap price…" "That won't be necessary. So what's your question?" "Well could you tell us what is light?" "Well that's a tough question. Let me start off with the basics. Like sound, light is a wave. Sound is a longitudinal wave (stretches and compression): And light is a transverse wave (like a water wave). Just to clarify for those who have some knowledge of sound, sound needs a medium to travel. Sound can travel in air, wood, steel, and water, but it cannot travel in space. So when you hear those explosions of star ships in star trek, you now know that in real life you wouldn't hear anything. Light however, can travel in a vacuum (absence of any matter). We know this because we can see light in space, and space is a vacuum. Now, getting back to your question Light not only acts as a wave, but it sometimes acts as a stream of particles. It has a dual nature. Characteristics of particles include that light travels in straight lines and in a beam. In the modern theory of light, we think of light to be a series of packets of energy. These packets have no mass and carry quantified amounts of energy." "Ah yes. Well that is quite a mouthful Einstein. So when you say we're not sure exactly what light is, you mean you have no idea?" "Exactly. I do have an idea that seems to explain a lot, but not everything. I would explain it to you but I'm afraid I would lose your attention." "What, who … oh yes,... lose my attention. Yes well you certainly did. Well Al, can I call you that?" "Of course, you know down at the disco they call me funky jam'in Aly. You should know that, after all, you are the head Afro king at the disco." "Ah maybe we shouldn't be talking about that right now, our reader may lose respect for both of us. Well Albert could you tell me about some of the properties of light?" "Of course I can…" "Just wait a sec, this is the point where I'm supposed to say 'click the button below to learn about the properties of light'" 
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Light is a
transverse wave