Refraction and Lenses - Mission RL4 Detailed Help

The diagram shows the path of light as it passes from air into, through, and subsequently out of a transparent material. Use the diagram and Snell's law to determine the index of refraction of the material. Enter your answer accurate to the second decimal place.


 
Snell's Law of Refraction:
The refraction of light towards or away from the normal follows a very predictable mathematical relationship known as Snell's law.
 
n1 • sin Θ1 = n2 • sin Θ2

where n1 and n2 are the indices of refraction of the two individual media and Θ1 and Θ2 are the angles of incidence and refraction within those media. Knowing any three of the four quantities in the equation allows one to predict the fourth variable.


 
The diagram shows the path of a light ray as it enters and finally exits a polygon consisting of an unknown material. The angle of incidence upon entering the material is 0 degrees; this is the one case in which light passes across a boundary without refracting. The refraction which occurs takes place as light exits the material. Angles between the light ray and the boundary are stated. These angles will need to be used to determine the angles of incidence and refraction and then to calculate the index of refraction.


 
The adoption of an effective strategy is critical to success on a question such as this one. The following strategy should prove useful:
  1. Determine the angle of incidence for the ray of light exiting the material. This angle is measured between the light ray and the normal line.
  2. Determine the angle of refraction for the ray of light exiting the material. Again, this angle is measured between the light ray and the normal line.
  3. Substitute the angles of incidence and refraction into the Snell's law equation (see Formula Frenzy section). Use 1.00 as the index of refraction of air. Substitute this value into the same side of the equation as the angle of refraction. Solve for the index of refraction of the unknown material.

TIP: If the calculated n value is less than 1.0, then you likely have made an error. Check your work and try again.


 
The Minds On Physics program calculates answers accurate to the fourth decimal place. Your answer does not need to be that accurate. The program will allow you to have a 1 percent deviation from the right answer without being wrong. This means two things: 1) Enter your answer with at least three significant digits. 2) Do not round any numbers until your final calculation.


 

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