This how it works covers How It Works: Total Internal Reflection in Optical Fibres within Reflection & Refraction for GCSE Physics. Revise Reflection & Refraction in Waves for GCSE Physics with 15 exam-style questions and 15 flashcards. This topic shows up very often in GCSE exams, so students should be able to explain it clearly, not just recognise the term. It is section 6 of 13 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.
⚙️ How It Works: Total Internal Reflection in Optical Fibres
An optical fibre is a thin glass or plastic strand. Light enters at one end and hits the glass-air boundary inside the fibre at an angle greater than the critical angle. Because the angle exceeds the critical angle, ALL the light is reflected (none escapes through the sides). The light bounces from one side to the other, zigzagging along the entire length of the fibre without losing significant energy.
This is why fibre-optic internet is so fast: light signals travel at roughly 2 × 10⁸ m/s through the glass, carrying enormous amounts of data. Unlike electrical signals in copper wire, light in glass has virtually no resistance and doesn't generate heat, making it far more efficient for long-distance data transmission.
Practice questions for Reflection & Refraction
According to the law of reflection, the angle of incidence is:
Explain why a ray of light bends when it passes from air into water.