Lesson Plan

• Describe how light changes direction at the boundary between two transparent media.
• Explain the relationship between angle of incidence, angle of refraction and refractive indices using Snell’s law.
• Calculate the angle of refraction or refractive index for given values.
• Predict whether the ray bends towards or away from the normal when entering a denser or rarer medium.
• Interpret diagrammatic representations of refraction.

• Projector or interactive whiteboard
• Printed worksheet with refraction diagrams
• Ray‑box or laser demonstration set
• Refractive index table handout
• Rulers and protractors
• Calculator

Begin with a short video of a straw appearing bent in a glass of water to hook interest. Ask students what they already know about light changing direction when it enters a new material. State that by the end of the lesson they will be able to describe and calculate this behaviour using Snell’s law.

1. Do‑now (5') – Quick quiz on the definitions of normal, angle of incidence and refraction.
2. Mini‑lecture (10') – Explain refraction, speed change, introduce Snell’s law with a diagram.
3. Demonstration (8') – Use a laser and acrylic block to show the ray bending towards the normal; discuss why.
4. Guided practice (12') – Students solve worksheet problems applying Snell’s law while the teacher circulates.
5. Group activity (10') – Using the refractive‑index table, predict bending direction for several material pairs and justify.
6. Check for understanding (5') – Exit ticket: one calculation and one short explanation of the bending direction.

Summarise the key points: definition of refraction, Snell’s law, and how the refractive index determines the direction of bending. Collect exit tickets to gauge mastery and assign homework to complete a set of Snell’s law problems from the textbook.