State the laws of refraction. What is dispersion of light? Explain it with a diagram.

1. 1 · Define refraction in one line. Refraction is the bending of light at the boundary of two media, due to a change in its speed.
2. 2 · Write the two laws.
   • The incident ray, refracted ray and normal lie in the same plane.
   • Snell's law: sin i / sin r = μ₂/μ₁.
3. 3 · Define dispersion. Splitting of white light into seven colours, VIBGYOR, when it passes through a prism.
4. 4 · Draw the prism. [Diagram: white light entering a prism and a spectrum on a screen, red at the top and violet at the bottom]
5. 5 · Give the reason. The refractive index differs for each colour: violet (short wavelength) bends the most, red (long wavelength) the least.
6. 6 · Real-life link. A rainbow after rain is sunlight dispersed by raindrops.
7. 7 · Close in one line. Refraction bends light, and the different bending of each colour causes dispersion.

Scoring tip: Write Snell's law as a formula, and label red and violet in the right places on the prism diagram.