Revise: Refraction of Light
The nature and velocity of light, the laws of refraction, refractive index, critical angle and total internal reflection.
Refraction bends light at a boundary because its speed changes; denser medium bends toward the normal.
A straw looks bent at the water surface due to refraction.
Snell's law: n₁ sinθ₁ = n₂ sinθ₂.
Light at 40° from air into glass (n=1.5) refracts to about 25.4°.
n = c/v; higher n means slower light in that medium.
Diamond's n = 2.42 gives a speed of about 1.24×10⁸ m/s inside it.
sinθc = 1/n; beyond the critical angle, total internal reflection occurs.
Glass (n=1.5) has a critical angle of about 41.8°.
Light has both wave and particle properties (wave-particle duality).
A prism splits white light into a rainbow, showing its wave nature.
c = fλ; light travels at ≈3×10⁸ m/s in a vacuum, slower in any medium.
We see the Sun as it was about 8 minutes ago.