ICSE Class 10Physics
⏱️ 15 min readRefraction of Light
Light bends towards the normal when passing from rarer to denser medium (speed decreases).; Total Internal Reflection (TIR) requires: light travelling from denser to rarer medium and angle of incidence > critical angle.
⚡ Essential Formula / LawCore Syllabus Rule
Snell's Law: μ = sin i / sin r | Critical Angle: sin C = 1 / μ | Shift = t (1 - 1/μ)
🎯 High-Yield Syllabus Checkpoints
- 1Light bends towards the normal when passing from rarer to denser medium (speed decreases).
- 2Total Internal Reflection (TIR) requires: light travelling from denser to rarer medium and angle of incidence > critical angle.
- 3Lateral displacement depends directly on thickness of slab, refractive index, and angle of incidence.
🚨 Examiner Traps & Common Mistakes
⚠️ Common Student Pitfall
Writing TIR occurs when i = C (at i = C, the refracted ray grazes the boundary at r = 90°).
⚠️ Common Student Pitfall
Assuming refractive index has units (it is a dimensionless ratio of speeds).
📚 Verified Technical Definitions
Critical Angle
The angle of incidence in the denser medium for which the corresponding angle of refraction in the rarer medium is exactly 90°.
Total Internal Reflection
The complete reflection of a ray of light within a denser medium when the angle of incidence exceeds the critical angle.
Spaced Repetition Protocol:
Day 1Day 3Day 7Day 21