HelpContactFor teachers and institutes
>_StemPy Lab
Mock TestsClasses

>_StemPy Lab

Learn. Solve. Code the solutions. Test yourself.

Live examsFree mock exams, timed and rankedEveryone starts together, and your score and rank come the moment it ends.See the exams →

Learn

  • Physics
  • Chemistry
  • Mathematics
  • Biology
  • Python Programming
  • Statistics & Data Science
  • Classes
  • Groups

Practice

  • Problems
  • Quizzes
  • Mock Tests
  • Prepare for an Exam
  • Question Sets
  • Exams
  • Certificates
  • Python Labs
  • AI Practice Generator
  • Student-Created Tests

Community

  • Discussions
  • Resources
  • Notes
  • Glossary
  • Blog

Account

  • Log in
© 2026 senLearn. All rights reserved.HelpAboutContactPrivacy PolicyTerms of UseRefund Policy
  1. Glossary
  2. /Physics
  3. /Snell's Law

What is Snell's Law?

In short

Snell's law says that when light passes from one medium into another, the sine of the angle of incidence divided by the sine of the angle of refraction is a constant for the two media.

In simple words

In symbols, n1sin⁡θ1=n2sin⁡θ2n_1 \sin\theta_1 = n_2 \sin\theta_2n1​sinθ1​=n2​sinθ2​, where n1n_1n1​ and n2n_2n2​ are the refractive indices and both angles are measured from the normal. Light entering a denser medium bends towards the normal. Light entering a rarer medium bends away from it. A ray that hits the surface along the normal is not bent at all.

Example

Light goes from air (n=1.00n = 1.00n=1.00) into water (n=1.33n = 1.33n=1.33) at 40∘40^\circ40∘ to the normal. Then sin⁡θ2=sin⁡40∘1.33=0.483\sin\theta_2 = \dfrac{\sin 40^\circ}{1.33} = 0.483sinθ2​=1.33sin40∘​=0.483, so θ2≈29∘\theta_2 \approx 29^\circθ2​≈29∘.

Also searched as: law of refraction.

Learn it properly

  • Lessons on this topic
  • Practise problems
  • Test yourself

Related terms

  • Refractive Index
  • Total Internal Reflection

← All glossary terms

Learn it in

  1. Refraction of LightClass 9 to 10
All lessons on this topic →

Practise

  1. A science museum shows light in a tall glass tank that holds two clear liquids which do…Hard
  2. A ray falls from air on to a flat surface of flint glass (n = 1.6)…Hard
  3. A fisherman looks at a fish in clear water and wants to hit it with a spear…Medium
  4. A swimming pool is 2.7 m deep. How deep does it seem when you look straight down into…Easy
All problems on this topic →

Quick questions

  1. Six statements about total internal reflection are given below. (i) A diamond sparkles…Hard
  2. The figure shows a tank holding water of depth 20 cm and refractive index 4/3, above a…Advanced
  3. A ray of light travels between glass of refractive index 1.50 and water of refractive…Hard

More Physics terms

  1. Acceleration
  2. Acceleration Due to Gravity (g)
  3. Adiabatic Process
  4. Amplitude
  5. Angle of Incidence
  6. Angle of Reflection
All Physics terms →

Preparing for an exam?

Pick your exam to see its syllabus, where you stand in each unit and what to practise next.

See exam preparation