Snell's law, the critical angle and total internal reflection
"Snell's law, the critical angle and total internal reflection" is a free, interactive Class 12 Physics simulation for NEET and JEE, built on the lesson "Total internal reflection" in Ray Optics and Optical Instruments. Change the angle of incidence. Some light is reflected and the rest is refracted; the brighter ray carries more light. Switch the direction of travel and tilt it again. JEE Main asked 66 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
From the lesson Total internal reflection in Ray Optics and Optical Instruments. Change the values and watch what happens.
In JEE Main
42 shifts analysed
66 questions from Ray Optics and Optical Instruments across the 42 JEE Main shifts Lumi has analysed (2017–2026).
The idea behind it
NCERT § "Total Internal Reflection"
- When light travels from a denser to a rarer medium, the refracted ray bends away from the normal; at the critical angle i_c the refracted ray grazes the surface (r = 90°).
- For incidence greater than i_c there is no refracted ray and all the light is reflected back into the denser medium: total internal reflection.
- Two conditions are needed: light must go from denser to rarer, and the angle of incidence must exceed the critical angle.
- For a denser medium of refractive index n relative to the rarer one, sin i_c = 1/n. For glass of n = 1.5 in air, i_c is about 42°.
- Since n = c/v, the critical angle can also be found from sin i_c = v_denser / v_rarer.
- Optical fibres use total internal reflection: a core is surrounded by cladding of lower refractive index, so light entering the core is reflected again and again along its length with very little loss.
- Bundles of optical fibres (light pipes) are used to transmit and receive signals in telecommunication and to look inside the body in medical examinations.
Questions
3 answers
- What does the "Snell's law, the critical angle and total internal reflection" simulation show?
- Change the angle of incidence. Some light is reflected and the rest is refracted; the brighter ray carries more light. Switch the direction of travel and tilt it again.
- Does JEE Main ask questions from Ray Optics and Optical Instruments?
- Yes. JEE Main asked 66 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
- Is this simulation free?
- Yes. It is free and runs in the browser on a phone or a laptop. It belongs to the lesson "Total internal reflection" in Ray Optics and Optical Instruments (Class 12 Physics).
Embed this simulation
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