refraction!

Refraction is the change in light speed due to change in medium! Refraction is dependent on the speed of light in the medium it's travelling through. We use the equation n=c/v, c standing for the speed of light in a vacuum which is 3x10^8m/s, v for the speed of light in the medium and n for the index of refraction. We used this equation to find the speed of light in air (n air) which is 1, by dividing 3x10^8m/s by 3x10^8m/s (c/n) and since the meters per second cancels out there is no units for the index of refraction. n and c have an inverse relationship meaning as the index of refraction goes up, the speed of light in a vacuum decreases. 

We can apply Snell's Law to refraction, which is n1Sinϑ1=n2Sinϑ2. To determine the direction of the refracted ray we can use our equation and plug in all the numbers we know in order to solve. The pencil goes from air to water, so air's index of refraction is 1 by using the equation n=c/v and dividing the speed of light by 3.0x10^8m/s, then to find the index of refraction of water you use the same equation but instead plug in 2.25x10^8m/s for v and get 1.33. If the angle the pencil is coming at is 60 degrees from the water, Theta1 would be 30 degrees. The pencil is going from fast to slow so n1<n2 and ϑ1>ϑ2.If i stuck my pencil perpendicular to the surface, there would be no bending since that is the normal. The light is coming from the top of the room, so if i use Snell's Law i can find the angle water bends the pencil at! It would bend more to the center or normal so to the left a little. Here's the work! vv 

We can also use Snell's Law to find the critical angle of object that go from a slow to fast medium such as water to air if the light source is coming from the water. This time n1 would be greater than n2 and we'd set it up as sin-1(1/1.3). 

We also learned about light that goes through different shaped lenses. An object in front of a lens in the shape of a long oval with light will send a ray parallel to the ground, then once it hits the lens, it travels towards the focal point on the images side going down. A parallel ray is parallel to the optic axis, meaning that light that hits there, will stay there. The focal ray will go through the focal point and then bend parallel to the optic axis. Light that hits the focal point on the object's side will travel downwards, then hits the normal coming from the lens and travel parallel to the surface. Another ray that hits the center in the middle of the lens will travel down and they will all meet causing the image to be ral and inverted because it shows up upside down and enlarged. I hope that makes sense! :]