Unit 10 - Light Properties (Reflection)

Today we learned a whole bunch! All of what we learned was about light and we focused on reflection. We did a lot of cool demos in class today involving colors of lights. Light colors are different from pigments, like paint. When light colors interact they don't combine to form colors like pigments do. For example when a yellow light hits a blue screen the resulting color is black, for pigments when yellow and blue are added together the resulting color is green, see the difference?

Here is a picture of the colors we learned about. The big circle colors red, blue and green are primary colors, the small colors magenta, yellow and cyan are the complimentary colors. When you add red, blue and green together you get white.

 Today we played around with color for a while. We had 3 projectors with the colors red, blue and green. 2 of the projectors would go on and then we would see what the resulting color would be. Then we would look at a worksheet that had problems like what color would be produced when yellow was shone onto a yellow screen. The answer would be yellow. It all has to do with reflection and absorption 

We learned that there are two types of reflections specular and diffuse. Specular reflection is when a surface is relatively smooth compared to the wavelength of the wave (reflection comes off as it is) . Diffuse reflection is when the surface of an object is bumpy or rough when compared to the wavelength of the wave, ex. light.

 White light is light that has all the frequencies ROYGBIV. White reflects while black absorbs. Shadows are places with an absence of light. The big idea that we learned today is the idea that you can only see light if it is reflected to your eyeballs. 

We learned about things about the earth that I have always wondered about like why the sky is blue and why the ocean is blue. The sky is blue because scattering of the blue wavelengths in the upper atmosphere due to nitrogen. The ocean is blue because water absorbs lower frequency lights. Absorbs ROY and then GBIV is left. Rainbows are because of dispersion. Light bends inside of a raindrop and rainbows are always opposite the sun.

The law of reflection is that the angle of incidence equals the angle of reflection; all angles are relative to the normal. The normal is perpendicular to the surface. Object distance= do= distance from object to mirror /lens. Object height= ho= height of object.  Image distance= di=distance of image to mirror/lens. Image height=hi=height of image. Another thing we learned is that unless there is fog in the air it is not possible to see a beam of light from the source because it is now directly going to your eyes.