# Abstract

In the 18th century, Newton, with some trepidation, announced light was a particle. Others disagreed. Through the 19th century they believed, with strong justification, that light was a wave. At the beginning of the 20th century Einstein discovered it was both. Today the photon has its place in the standard model as one of the fundamental particles of nature. For this lab, we will be studying light at its behavior using the ideas of Geometric optics. This is an abstraction useful for discussing the path along which light propagates through lenses.

At every boundary, a wave (sound, light, anything), undergoes transmission, reflection, and absorption. A brick absorbs many colors, reflects a few, and transmits none. A mirror reflects almost everything, but there is always some absorption and since light can have almost any energy, there’s the possibility of some transmission. Glass, depending on conditions transmits most light, but again there is always some absorption and reflection.

Bricks don’t make the most interesting optical studies, but glass, or any transparent material does. Simplifying assumptions; Geometric optics; light travels in straight lines called rays and is reflected and refracted once, in straight rays. Transmission is not quantitatively studied, we are not interested in how much light is transmitted, we interested in how it behaves, refraction.

# Procedure

• Clicked on the blue plus sign to enter video analysis mode. Used the ‘Create Measurement Tool’ and clicked on the ‘Angle Tool’. All angles are measured from the normal, a line perpendicular to the face of the lens.
• At the bottom of the capstone display are a set of video controls, used them to advance the video. Right above it is a slider that does the same thing and easier to use.
• Made sure the video was in the first frame. There are 3 rays visible, the incident ray, the reflected ray and the refracted ray which are rays in this study
• Aligned the base of the tool along the face of the half round lens with the pivot point on the center of rotation. Rotated the other arm of the tool until the angle reads 90 degrees. This is the normal to the lens surface.
• Rotated the arm along the lens until it aligns with the incident laser ray. Leaving the normal alone and record the angle in the table.
• Rotated the same arm, to the other rays of interest and read the angles. Needed angles from the normal so they should always be acute. Subtract from 180 to find angles on the other side of the normal.
• Advanced the video using the slider or VCR controls and repeat this process for 10 angles of incidence, recording the angle of incidence and the angle of reflection and the angle of refraction.

# Analysis Graph

The graph shows a linear relation between angles. Therefore, Snell’s law would be a relationship between paths taken by these rays in crossing the surface of separation.

# PROCEDURE TWO

• Use the Angle tool to measure both sets of angles, incident and refracted.
• Calculate the index of refraction for the prism, twice. Show your calculations, once going in, once coming out.

Angle of incidence is 39.73

Angle of refraction 25.48

# Conclusion

The refractive of the material is sine of incidence divided by sine refraction

In this case it is 1.50 the material is therefore flint glass.