# 3B Scientific U14600 Optics on magnetic boards User 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.