Explore BrainMass

Light Refraction and Reflection of a Laser

The drawing shows a crown glass slab with a rectangular cross-section. As illustrated, a laser beam strikes the upper surface at an angle of 60.0 degree. After reflecting from upper surface, the beam reflects from the side and bottom surfaces. (a) If the glass is surrounded by air, determine where part of the beam first exits the glass, at point A, B, or C. (b) Repeat part (a) assuming the glass is surrounded by water.

(See attached file for diagram)


Solution Preview

a) Please see the diagram given below. Here the refractive index (m) of Crown Glass with respect to air is taken as 1.52. To determine as to from where the light ray would first emerge, we must realize that the light ray would emerge only when the angle of incidence at any of the points A, B or C is less than the critical angle. If the angle of incidence is equal to or exceeds the critical angle, there would be total internal reflection and the light ray would not be able to come out.

To calculate the critical angle, we have:
Sin C = 1/m; where C is the Critical Angle and m ...

Solution Summary

This solution contains an annotated diagram of the laser beam path in the glass and contains step-by-step calculations to determine if the beam exits the glass at point A, B or C when surrounded by air or water.