Investigating Refraction

Investigating Refraction

Aim: Find the critical angle and refractive index for plastic using a

graphical treatment for my results.

Introduction: The Refractive Index is how the much a material bends

the light. In this experiment I will be looking at the how much the

angle of incidence gets refracted and I will multiply my results by

sine. I will plot a graph from my results and, using a line of best

fit, I will calculate the size of the angle of incidence in order for

the refracted angle to be equal to 900 (critical angle). I will then

calculate the refractive index by using Sine I and Sine R. I will be

looking at light going from glass to air (from a dense medium to a

lighter one).

Theory: Incident ray: Ray of light before refraction. Angle of

refraction (R): Angle between refracted ray and normal at point of

incidence. Angle of incidence (I): Angle between incidence ray and

normal at point of incidence. Point of incidence: Point at which

incident ray meets boundary and becomes refracted ray. Critical angle:

The particular angle of incidence of a ray hitting a less dense

medium, which results in it being refracted at 900 to the normal.

Normal: A line at right angles to boundary through chosen points.

There are two main laws of refraction of light: 1. The refracted ray

lies in the same plane as the incident ray and normal at the point of

incidence. 2. (Snell's law). The ratio of the sine of the angle of

incidence to the sine of the angle of refraction is a constant for two

given media. This constant is the refractive index (n). When referring

to light, this is also known as the optical density and, as with

refractive index in other cases, can also be calculated by dividing

the velocity of light in one medium by its velocity in the second

medium. The formula for calculating the refractive index is: [IMAGE]

I will draw a graph of Sine I and Sine R.