Total Internal Reflection and Refraction Quiz

Total Internal Reflection

• Total internal reflection occurs when light travels from a denser medium to a less dense medium at an angle of incidence greater than the critical angle.
• Light does not refract but reflects back into the denser medium.
• This phenomenon is useful in fiber optics, applications in cars, and tools for viewing the human body.
• The critical angle is the specific angle of incidence at which the angle of refraction is 90°.
• Refractive index of air = 1.00
• Refractive index of water = 1.33
• Critical angle for water entering air = 48.8°

Angle of Refraction

• Light refracts when it changes from one medium to another.
• Refraction happens at an angle.
• If the angle of incidence is 90° (perpendicular to the surface), there is no refraction (no angular change).
• Light bends away from the normal when travelling from a denser medium to a less dense medium.
• Angle of refraction is always larger than the angle of incidence in this situation.

Critical Angle

• As the angle of incidence increases, the angle of refraction also increases.
• Eventually, the angle of refraction is 90 degrees
• The angle of incidence at this point is known as the critical angle.

Fibre Optics

• Fibre optics use total internal reflection to transmit light along thin glass fibres.
• Used in communication (phones, computers, TVs).
• Used in automotive industry instrumentation.
• Used in medical applications ( endoscopes).

Diamonds

• Diamonds sparkle due to their high refractive index.
• This high index results in a small critical angle (24.4°).
• Incident light undergoes total internal reflection many times, causing the sparkling effect.

Practice Questions

• Light travels fastest in a vacuum.
• Light speed changes when changing from one medium to another (e.g., air to water).
• Light changes its direction when moving from one medium to another. This is due to different densities of the two media.
• Refractive index describes how much a medium slows light down and is related to the material’s density.
• Light travels faster through a medium with a lower refractive index.
• Internal reflection occurs when light reflects off a surface, rather than passing through it, and occurs when the angle of incidence is greater than the critical angle.