Reflection And Refraction Lab

OBJECTIVE

The objective of this experiment is to study refraction and reflection and also to use Snell's law correctly to determine the optical properties and indices of refraction for a prism.

DATA

All data is included in an excel spreadsheet, attached to this write-up.

Some uncertainties that see probable in the case of general human error are the basic visualization of the location of the pin, the measuring of the angles with a protractor, the possibly imprecise way to draw the reflected and incident rays and a general error in calculation. It is also possible that some uncertainties were caused by equipment imperfections, such as the mirrors being warped or the pins being bent. Also, some protractors were more precise and easily read, while others were not.

RESULTS

µ=∑(x) , where µ= mean in cm (also referred to as ), ∑= summation, x= the actual numbers obtained in the data set recorded in ohms, n= the number of data points.

Ex: (1.391+1.766+1.431+1.643+1.530+1.209+1.447+1.486)/8 = 1.488

n1sinθ1=n2sinθ2, where n1= the indices of refraction of air (denoted as 1), θ1= the angle from the parallel that corresponds to n1, n1= the indices of refraction of the prism, θ2= the angle from the parallel that corresponds to n2.

Ex: 1Sin34=n2Sin23

n2=1.431

There are no graphs associated with this experiment, however there are pictures where the angles measured and that rays determined are drawn in a labeled. These pictures are attached to this write-up.

DISCUSSION

We are first observing the reflection of a pin from a flat mirror. Reflection is defined as the rebounding of a particle or wave due to encountering a barrier or a change in the medium. An original pin was placed at a chosen distance in front of a flat mirror. While looking into the mirror from various chosen angles, additional pins were then placed in the path of the reflected ray and the angle from the perpendicular was measured. Since we know that the law of reflection applies we can then determine the position of the incident ray. If the original pin is in the path of the determined incident ray, then we can assume that the pin was places accurately in the path of the reflected ray.

When you place a real object in the position of the virtual image and they look like they are in the same position, regardless of the direction they are viewed from, you have just determined the location by parallax. This property stated that there is no obviously motion of the two objects, regardless of the direction they are viewed from, only if the two objects are at the same location. To determine if the locations of the two objects were equal, the distance from the original pin to the mirror surface and the real object to the mirror surface is measured. If the locations of the two objects are the same these measured distances would be equal.

We are secondly observing the general properties and characteristics of refraction. Refraction is defined as the change in speed of a wave due to being in a different medium. Pins were placed in a linear fashion along a chosen side of a square prism at a designated angle from the perpendicular. While viewing the virtual image through the opposite side of the square prism, more pins were placed in line with the virtual image, giving the illusion that there was only a single pin being viewed. To show the angle of refraction, the sites where both lines meet the sides of the prism were connected. All angles were measured from the perpendicular. Using Snell's Law and the measured angles, the desired index of refraction (n) can be determined. The index of refraction for air is set to 1 and is denoted as the variable n1.The index of refraction for the medium, n2, was found for both sides of the square prism. Since the square prism is a consistent medium, the indices of refraction for both sides should be equal. The process was repeated four times and the indices of refraction were compared. A total variation of .232 was found for the square prism, when considering all measured and calculated values. This number is larger then desired possibly due to a considerable amount of unknown sourced of error.

A triangle prism is then used instead of the square prism and the same procedure is taken. A total variation of .557 was found for the triangle prism, when considering all measured and calculated values. This number is much larger then desired; this number is also possibly due to a considerable amount of unknown sourced of error.

Some specific sources of error that seem to be apparent in our data observed and calculated are the imprecision of basic protractors that were used. Although this would not make a massive margin of error, it could change the margin of error by a few tenths, which is approximately what the values seem to be off by overall. Although it was not observed that the mirror that was bent or warped, the original mirror used was cracked and had to be replaced. If one was to overlook even a minuscule fracture in the

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