After this lesson, you should be able to:

• Define refraction, refractive index and optical density
• Explain that during refraction the speed of the wave changes but its frequency remains the same
• Identify the terms normal, angle of incidence and angle of refraction in appropriate ray diagrams
• Express Snell’s law as n₁ sin \(\theta\)₁ = n₂ sin \(\theta\)₂
• Apply Snell’s law to problems involving refraction of light
• Draw ray diagrams for light passing from a medium of higher refractive index to one of a lower one and vice-versa