Physics Unit 10 (Part 2)

 We learned a lot in class today, which, in all honesty, was pretty painful. We learned a lot more about lights and reflection, which was both interesting and incredibly confusing, so please bear with me as I attempt to explain everything.

 First of all, there's this type of light called white light. White light has all frequencies of ROYGBIV, which means that it has the frequencies of all the colors of the rainbow. When an object is a certain color, that means that the object is reflecting the color that you are seeing, while absorbing all the others. Also, black absorbs all the colors while white reflects them, so if you are ever planning on walking around in a desert, make sure you're wearing a white shirt when you do so. Wearing a white shirt will keep you a lot cooler than if you were wearing a black shirt. Now that you (hopefully) understand white light, let's move on to colored lights (because I am unbiased like that). So, in the pictures on the left, you can see my teacher, Mr. Blake, standing in red light and green light, and even though it might be hard for you to determine, he's wearing a red shirt. So, since his shirt is red, you know that it is absorbing all other colors except for red, which is being reflected. When he's standing in the red light, his shirt is going to look red, because it is still reflecting red back. However, when he is standing in the green light, his shirt will look black. The reason his shirt looks black, is because there is no red light for it to reflect at all, which causes it to look black instead.

The picture on the left is of the Color Wheel of Light, which has the primary colors, also known as the main colors of light. It also shows what color two lights make when they are shining into each other, as well as the complimentary colors, which are colors on the opposite sides of the wheel that, when added together, make the color white. Unfortunately, you can't think of the color wheel of light as anything other than related to light. I know that it's confusing, and you want to think of it with the same concept you would paint, but when you mix the colors together, they make white, not brown.



 This next picture, show my Mr. Blake's three shadows, which are the results of shining three different lights at him, a red light, a green light, and a blue light. As you hopefully noticed, those are the primary colors that I listed above. The order of the lights from left to right were green, blue, and red. You can tell, because the shadow on the left is cyan, which means that it had the lights green and blue on it, while Mr. Blake blocked the red light. The middle light is yellow, which means that green and red were shining together to create that color while Mr. Blake blocked the blue from interfering. Lastly, there is magenta, which is made up of red and blue, with Mr. Blake blocking the green light. You can also see that the sort of square around the shadows is white-ish, which is a result of the three primary colors mixing together.



A common misconception people have is why the sky and ocean are blue. Most people think that they're blue because they are reflecting each other, but that is actually wrong. The sky is blue (actually more of a violet color, but we can't really see that), because blue wavelengths are scattering in the atmosphere due to nitrogen. The ocean is blue because the water absorbs the ROY in ROYGBIV, leaving the green, blue, indigo, and violet to be reflected. Also, a really cool fact that Mr. Blake told us today had to do with why fish are red, since you'd imagine they would want to be darker and not draw attention to themselves. In actuality, because the red, orange, and yellow frequencies are being absorbed in the water, there is no red light to reflect off of the fish. This means that the fish appears to be black in the water, and keeps it safe (isn't that awesome?!).

 We learned one of the Laws of Reflection, which stated that an angle of incidence equals the angle of reflection (works for all mirrors). Also, all angles are relative to the normal, which is perpendicular to the surface. This means, that when you shine a light at a mirror and you imagine a perpendicular line coming up from where it hits the mirror, the angle the light is reflecting at will be the same as the angle of the original light... if that made any sense at all. If you look at the picture to the left, you can see Mr. Blake shining a laser at a mirror. The light that is coming out of the laser is the light with the angle of incidence. The point where you can see that the laser hit the mirror is where the normal would be. You can see where the light reflects off the mirror, which is the angle of reflection. Relative to the normal, both angles will be equal.

Lastly, we learned that while you can't see light normally, when it is foggy, you can. This is (I believe) because of the light reflecting off the little droplets, which then go into your eyes, allowing you to see them (doesn't the picture on the left look amazing, they're kinda like extremely long, narrow lightsabers!!).

So, if you can only take one lesson out of this whole blogpost, let it be this: next time your car breaks down in the middle of an incredibly foggy forest at night, instead of heading into the woods to inevitably find the creepy cabin and get yourself killed, pull out your laser and have a lightsaber battle with your friends until morning (or the fog goes away, whichever happens first).