3 - Critical Angle Restart the simulation (click the bottom right yellow button). Light source: Ray. Material above: Water. Material below: Air. Start with an angle of incidence of about 60 degree and slowly decrease it. 17. The refracted ray disappears when the angle of incidence is larger than which value? When the angle of incident is larger than the critical angle, the light hits the air' surface and it 'bounces back' into the water. 18. What is the name of the optical effect? Select Material above: Mystery B. Material below: Air. Repeat the procedure 19. What is the index of refraction of Mystery B? Open the link https://en.wikipedia.org/wiki/List of refractive indices 20. Which material best matches the result of your calculation in question 19