This key facts covers Total Internal Reflection within Reflection & Refraction for GCSE Physics. Revise Reflection & Refraction in Waves for GCSE Physics with 15 exam-style questions and 15 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 5 of 13 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 5 of 13
Practice
15 questions
Recall
15 flashcards
💎 Total Internal Reflection
What it is: When light reflects COMPLETELY inside a denser medium instead of refracting out.
Two conditions required:
- Light travelling from a denser → less dense medium (e.g., glass to air)
- Angle of incidence > critical angle
Applications:
- Optical fibres — light bounces along the inside by TIR, carries data at the speed of light
- Endoscopes — doctors see inside the body without surgery
- Diamonds — sparkle due to a high critical angle and many TIR reflections inside
- Binoculars/periscopes — use glass prisms where TIR redirects the light path
Quick Check: A ray of light hits a mirror at 40° to the surface. What is the angle of reflection?
The angle to the surface is 40°, so the angle of incidence (measured from the normal) = 90° − 40° = 50°. Therefore the angle of reflection = 50°.