Total internal reflection

The title of the Project: Total internal reflection

Purpose of the work:

  • Identify conditions for total internal reflection.

Practical part

Choose “Intro” to start the virtual experiment. 

This is a little instruction to the virtual experiment.

Virtual experiment.

Step 1. Turn on the laser. Position the protractor along the normal line.

Step 2. Place the instrument for measurement the intensity on the reflected ray. 

Step 3. Increase the index of refraction of the incidence medium. Gradually decrease the index of refraction of the refraction medium. What happens? 

Step 4. Notice that at some point the intensity of the reflected ray became 100%. It is called total internal reflection. Make a conclusion.

Step 5. Increase the angle in incidence. What happens? The intensity of the reflected ray is still 100%. 

Step 6. Decrease the angle of incidence. What happens? At some point some part of the ray gets refracted. The angle at which it happens is called the critical angle. 

Step 7. Make a conclusion.


There are two conditions for the total internal reflection to happen. First, the incidence medium must be denser than the refraction medium. Second, the incidence angle must greater than the critical angle. The critical angle can be found by taking arcsinus of refractive index of the second medium divided by the refractive index of the first medium (medium of incidence).