Refraction and Lenses - Mission RL4 Detailed Help

The diagram below depicts an incident ray approaching an air-water boundary. Use the given indices of refraction to determine the angle of refraction (in degrees) for this light ray. Enter your answer accurate to the first decimal point.

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 two media (shaded yellow and pink), a boundary line (solid black line) and an incident ray (red line with arrowhead). Indices of refraction for the two media are stated on the diagram. The angle of incidence will need to be measured using a protractor. Be sure to measure the angle between the incident ray and the normal line.

The adoption of an effective strategy is critical to success on a question such as this one. The following strategy should prove useful:
  1. Measure the angle of incidence for the ray of light approaching the boundary. Place a protractor on top of the screen and measure the angle between the incident ray and the normal line.
  2. Substitute the angle of incidence value and the indices of refraction into the Snell's law equation (see Formula Frenzy section).
  3. Rearrange the equation algebraically so that the sin Θ2 is by itself on the right side of the equation. Evaluate the left side of the equation using your calculator.
  4. Take the inverse-sine of both sides of the equation in order to solve for the value of Θ2.

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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