4 • Critical Angle / Total Internal Reflection

Define Critical Angle (c)

The angle in a denser medium that results in an angle of 90° in the rarer medium

Label This Diagram

The Critical Angle

a - critical angle

b - 90°

c - air

d - glass

Label This Formula

Refractive Index - Critical Angle

n - refractive index

c - critical angle

What page of the log tables can you find the Refractive Index (Critical Angle) Formula?

60

Define Total Internal Reflection

When a light ray travelling from a denser to a rarer medium at an angle greater than the critical angle is completely reflected

Name 3 uses of Total Internal Reflection

• Optical Fibre Cables

• Prisms

• Mirages

Label This Diagram

The Optical Fibre Cable

Demonstrate the use of an Optical Fibre Cable • 1

Outer glass layer has a lower density than the inner glass core

Demonstrate the use of an Optical Fibre Cable • 2

Light passes through the core and undergoes TIR

Demonstrate the use of an Optical Fibre Cable • 3

Light cannot escape the glass core

Identify the angle at which this prism is rotated at

90°

Identify the angle at which this prism is rotated at

180°

Label This Formula

Relative Speeds

n - refractive index

c1 - speed in medium 1

c2 - speed in medium 2

What page of the log tables can you find the Refractive Index (Relative Speeds) Formula?

59