Rami Arieli: "The Laser Adventure" Snell Game Applet
Applet: Snell's Shooting Game

You are in the room on right (as seen from above),  and your mission is to Hit the target located in the left room.
You have a laser, which emit a short laser pulse of high energy.
Each time you have only one shot !
Between the rooms, the wall is opaque, but there is a transparent glass (n = 1.5) cylindrical with 1 meter diameter (Seen as a circle in the picture).

  1. Position the laser in the room, with a click on the left button of the mouse. The location of the cursor is the new location of the laser.
  2. Mark the direction of the beam, by pointing on the glass cylinder, and click on the right button of the mouse.
As a result, a shot will be fired from the laser to the direction on the glass cylinder.
The computer will calculate the beam path, and show it on the screen.
It is prefered to think before the firing where to aim the beam ! 


  1. For the default values of n, when the laser and the target are under the horizontal diameter, do you have to aim the laser above or under the horizontal diameter, in order to hit the target? Why?
  2. What are the conditions on the values of n, such that you can not hit the target, anywhere in the room?
  3. As a conclusion from this activity, can there be a total internal reflection in a transparent glass ball? If yes, under what conditions?
  4. When n1>>n2, Is your answer to question 1 remains the same? Explain, and check possible cases.
  5. When n1 = n2 , the beam advance ___________ (fill in the blank). Is it possible to hit the target under these conditions? Explain.
  6. Can there be a case (under the simulation conditions) that the beam will be reflected back and hit the shooter? (check your answer with the simul;ation).
  7. Fill in the blanks:

  8. When n1>n2 _______________________________________________ .
    When n1<n2 _______________________________________________ .