3B Scientific U14600 Optics on magnetic boards - Manual (Page 4)

Exp.11: Semi-circular body
_
Light
incident at right angle to tangent
If a light ray perpendicular to the tangent
passes through a semi-circular body it will
not be deviated. The ray is refracted at
the point of emergence with the refraction
angle β, which is larger than α. It is bent
away from the normal. Partial internal
reflections occur at incident angles
smaller than the critical angle in the
dense medium.
Exp.12: Semi-circular body
_
Critical
angle
A pencil of light is projected along the
extension of a radius of the disc. The
semi-circular body is rotated until total
internal reflection occurs. The critical
angle α can easily be measured.
Exp.13: Triangular Prism- Total
internal reflection, 90° deviation
When the ray impinges the edge of the
triangular prism, it is totally reflected. If
the prism is slightly adjusted reflection
and refraction can be observed. The 90°
deviation is used in the design of some
modern periscopes.
Exp.14: Triangular Prism- Total
internal reflection, 180° deviation
The conditions for total reflections are
fulfilled on both edges of the prism. The
basic principle of prism binoculars is
demonstrated.