What is total internal reflection?

Total internal reflection occurs when light traveling from a denser medium to a rarer medium strikes the boundary at an angle greater than the critical angle, causing it to be completely reflected back into the denser medium.

What is the speed of light in... | Light (Optics) MCQ | Exambodh

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MediumQ. No. what-is-the-speed-of-light-in-water

What is the speed of light in water?

Q: What is the speed of light?

The speed of light in a vacuum is approximately 3 x 10^8 meters per second, denoted by the symbol c.

Last Updated: 30 Jun 2026

A3 × 10⁸ m/s

B2.04 × 10⁸ m/s

C2.25 × 10⁸ m/s

D2 × 10⁸ m/s

Correct Answer: 2.25 × 10⁸ m/sYour Answer: C

Explanation

Speed of light in different media is frequently tested in competitive exams. Option A is wrong. 3 × 10⁸ m/s is the speed of light in VACUUM not in water. In any material medium light slows down due to interaction with atoms. The ratio of vacuum speed to medium speed gives the refractive index. Option B is wrong. 2.04 × 10⁸ m/s is the speed of light in TURPENTINE OIL not in water. Turpentine oil has a refractive index of approximately 1.47. Students often confuse the values for different media. Option C is CORRECT. The image table states: पानी में प्रकाश की चाल — 2.25 × 10⁸ m/s. Water has a refractive index of approximately 1.33 (= 3×10⁸ / 2.25×10⁸ = 1.33). The speed of light in water is 2.25 × 10⁸ m/s. This is why objects in water appear closer than they actually are (due to refraction). Option D is wrong. 2 × 10⁸ m/s is the speed of light in GLASS not water. Glass has a refractive index of approximately 1.5 (= 3×10⁸ / 2×10⁸ = 1.5). Glass slows light more than water does because glass is denser and has a higher refractive index.

Important Notes

Speed of light in different media (m/s): Vacuum=3×10⁸ Water=2.25×10⁸ Turpentine oil=2.04×10⁸ Glass=2×10⁸ Rock salt=1.96×10⁸. Refractive indices: Water=1.33 Turpentine=1.47 Glass=1.5 Rock salt=1.54 Diamond=2.42. Formula: n=c/v. Higher n → lower speed → more bending of light. Glass minimum speed among common transparent media (exam context). Minimum speed mentioned in image = glass.

Light (Optics)

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Answer

2.25 × 10⁸ m/s

Exam Info

Asked in: SSC, Railway, Banking and other competitive exams.
Also asked in: RRB NTPC, CHSL, State PCS and online mock tests.
Topic: Light (Optics)

Light (Optics) FAQs

Common questions and clear answers for this topic.

What is optics in physics?

Optics is the branch of physics that studies the behavior of light, including its reflection, refraction, and interaction with lenses and mirrors.

What is the difference between reflection and refraction?

Reflection is the bouncing back of light when it strikes a surface, while refraction is the bending of light as it passes from one medium to another with a different optical density.

What is a lens?

A lens is a transparent optical device with curved surfaces that refracts light to converge or diverge rays, commonly classified as convex (converging) or concave (diverging).