Total Internal Reflection

Total Internal Reflection - Virtual Simulation
Qualitative

1. Open the simulation.

2. Move the beam of light and describe what you see.



3. What is total internal reflection?

Fiber Optics Lab - Virtual Simulation
Qualitative Analysis

1. Open the fiber optics simulation.

2. Move the light source outside the fiber optic. Change the angle of the beam by right clicking, holding the button on the white dot outside the light source and dragging it.

Is the fiber optic more or less optically dense than the air around it?? How do you know?


Is the index of refraction of the optic fiber greater than or less than 1? How do you know?


What happens to the beam inside the fiber optic if the light rays hit perpendicular to the fiber optic?


3. Move the light source into the fiber optic. Change the angle of the beam over the full range allowed. Describe what you see happening.





4. The simulation does not show this, but what also happens to a ray of light hitting a boundary at an angle besides being refracted when it enters the new medium?




Follow the links and answer the questions. Show your reasoning and your calculations.

Lesson 3: Total Internal Reflection
Boundary Behavior Revisited

1. Draw the reflected and refracted rays (use the law of reflection and Snell’s Law).

Lesson 3: Total Internal Reflection
Total Internal Reflection

2. Define total internal reflection (TIR) in terms of the behavior of light at a boundary.


3. Could TIR would happen for light traveling from water towards air? Why or why not?


4. Could TIR happen for light traveling from water (n=1.333) towards crown glass (n=1.52)? Why or why not?


5. What is the greatest possible angle of refraction? Why?



6. For each combination of media, which light ray (A or B) will undergo total internal reflection if the incident angle is gradually increased?

Lesson 3: Total Internal Reflection
The Critical Angle

7. What gives diamonds their sparkle? Is the cut of a diamond important? Why or why not?

8. Suppose that the angle of incidence of a laser beam in water and heading towards air is adjusted to 50-degrees. Use Snell's law to calculate the angle of refraction? Explain your result (or lack of result).

9. Aaron Agin is trying to determine the critical angle of the diamond-glass surface. He looks up the index of refraction values of diamond (2.42) and crown glass (1.52) and then tries to compute the critical angle by taking the

invsine(2.42/1.52).

Unfortunately, Aaron's calculator keeps telling him he has an ERROR! Aaron hits the calculator and throws it own the ground a few times; he then repeats the calculation with the same result. He then utters something strange about the pizza he had slopped on it the evening before and runs out of the library with a disappointed disposition. What is Aaron's problem? (That is, what is the problem with his method of calculating the critical angle?)




10. Calculate the critical angle for an ethanol (n=1.36)/air boundary .




11. Calculate the critical angle for an flint glass(light) (n=1.58) /air boundary.




12. Calculate the critical angle for a diamond (n=2.417)/crown glass n=1.52) boundary.





13. Some optical instruments, such as periscopes and binoculars use trigonal prisms instead of mirrors to reflect light around corners. Light typically enters perpendicular to the face of the prism, undergoes TIR off the opposite face and then exits out the third face. Why do you suppose the manufacturer prefers the use of prisms instead of mirrors?



Total Internal Reflection - Virtual Simulation
Quantitative

1. Open the simulation.

2. Choose "Refraction" from the menu.

3. Move the light source until you find the smallest angle of incidence which produces total internal reflection. This is the critical angle. Record this angle.

4. Move the light source so the light is refracted. Use Snell's law to find the index of refraction of the semicircular substance.

5. Calculate the critical angle from your answer to #4 and compare to the angle you measured in #3.

Fiber Optics Lab Revisited - Virtual Simulation
Quantitative Analysis


1. Reopen the fiber optics simulation.

2. Drag the light source outside of the fiber optic. Make measurements and determine the index of refraction (n) of the fiber optic. Right clicking and holding the mouse button down provides you with a tool to measure angles.









3. Using this index of refraction, calculate the critical angle for the fiber optic.






4. Move the light source inside the fiber optic. Change the angle of the beam by right clicking, holding the button on the white dot outside the light source and dragging it. Find the critical angle. How does this compare to the angle you calculated in #3?