IEMJEE Physics preparation: Refraction and Snell law — worked example and reasoning

Problem to solve

Light travels from air n₁=1 into glass n₂=1.5 at 30°. Find sin θ₂.

Try the problem before reading the answer. Record the requested quantity, relevant information and any interpretation choices. Keep this original practice example separate from official examination questions or previous-year papers.

Choose the governing principle

n₁ sin θ₁=n₂ sin θ₂; angles are measured from the normal.

Refraction changes propagation direction when a wave crosses media with different refractive indices.

Worked answer

sin θ₂=(1/1.5)×0.5=1/3.

The answer follows the stated model and the values in this question. Preserve exact expressions when given; if you use a numerical approximation, label it and keep sufficient precision until the final step.

Audit the reasoning

Check dimensions, direction and limiting behaviour. Ask whether the answer should increase or decrease when an input changes. A dimensional check is necessary in many calculations but cannot certify an omitted dimensionless coefficient or an inappropriate physical model.

A specific error to avoid here: Angles measured from the surface must first be converted to angles from the normal.

Explain before repeating

Write a short explanation linking the governing principle to the answer rather than copying the final line. Identify one assumption and explain how violating it would make this method unreliable. Use the linked worksheet for a new task, then return to this example after a delay and solve it without the answer visible.

Official sources and verification

Sources checked on 26 October 2026. A source’s date, programme and campus limit which claims it supports. Official pages may change after review.

1. UEM — IEMJEE examination information

   Historical examination pattern; verify the current cycle on the central portal.

2. NTA — explicitly labelled JEE Main 2026 syllabus

   Historical PCM syllabus reference. Lessons and exercises are independently authored, not official IEMJEE papers or verified 2027 paper predictions.

3. NCERT — official textbook catalogue

   Primary textbook reference for checking school-level concepts. This directory does not certify the independent lesson or establish IEM examination weightage.

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