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Waves · Chapter 5: Refraction and total internal reflection

Year 11 Science · About 18 minutes with activities · Turn your sound on

Chapter 5 · Refraction and TIR
Light follows the bendinside a glass fibre
Into glass: slowsbends toward the normal
Out into air: speeds upbends away from the normal
Ray-box laba semicircular glass block, ray aimed at the centre
Refracts outa little reflects
Skims the boundaryangle of refraction = 90°
TIRall the light reflects back
Core n > cladding nso TIR can happen at the edge of the core
Angle of incidence > θctotal internal reflection at every bounce

Chapter 5 recap

  • Refraction: the changing of speed of a wave when it enters a medium of different density. Slows → bends toward the normal; speeds up → bends away.
  • Snell’s law: n₁ sin θ₁ = n₂ sin θ₂. Angles are measured from the normal. Air 1.00 · water 1.33 · glass 1.50 · diamond 2.42.
  • TIR: from a more to a less optically dense medium, at more than the critical angle, θc = sin⁻¹(n₂ ÷ n₁). Optical fibres: core n > cladding n.
  • Next: Chapter 6 · Diffraction

How does light go round corners inside a glass fibre?

Chapter 5 · About 18 minutes · sound on

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