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Indian Navy 10+2 B.Tech Cadet Optics — practice questions

Explore 32 free Optics questions in Indian Navy 10+2 B.Tech Cadet Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Optics questions and exercises with answers

Showing questions 1–30 of 32.

The critical angle for total internal reflection at a glass-air interface is $42^\circ$. The refractive index of the glass is approximately:Read the answer and worked solution →A pendulum of mass m swings to amplitude angle θ. At the lowest point of swing, the TENSION in the string equals:Read the answer and worked solution →A car of mass 1000 kg moving at 36 km/h is stopped by brakes in 5 seconds. Average force exerted by brakes:Read the answer and worked solution →A body in equilibrium under several forces hasRead the answer and worked solution →A 0.5 kg ball hits a wall at 10 m/s and rebounds at 10 m/s. The impulse on the ball isRead the answer and worked solution →As per your syllabus, for a body of constant mass, the second law reduces to which form?Read the answer and worked solution →Cartesian sign convention: positive or negative?Read the answer and worked solution →True or false: the sign conventionRead the answer and worked solution →Complete the condition for total internal reflectionRead the answer and worked solution →Tap every example of total internal reflectionRead the answer and worked solution →Critical angleRead the answer and worked solution →True or false: optical fibresRead the answer and worked solution →Match each formula to what it describesRead the answer and worked solution →Converging or diverging?Read the answer and worked solution →Complete the definition of lens powerRead the answer and worked solution →Lenses in contactRead the answer and worked solution →Order the steps: solve a mirror problemRead the answer and worked solution →Assertion and reasonRead the answer and worked solution →Match each instrument to its magnifying powerRead the answer and worked solution →True or false: optical instrumentsRead the answer and worked solution →Which instrument does this belong to?Read the answer and worked solution →Two are true, one is notRead the answer and worked solution →Three of these are wrong. Find the one that holds.Read the answer and worked solution →Tap every statement true of refractionRead the answer and worked solution →Complete the prism relationRead the answer and worked solution →Flip and pair: symbol with meaningRead the answer and worked solution →Spot the one that does not belongRead the answer and worked solution →Reading the laws backRead the answer and worked solution →Order the reasoning: why an optical fibre worksRead the answer and worked solution →True or false: mirrors and lensesRead the answer and worked solution →

Worked practice questions

The critical angle for total internal reflection at a glass-air interface is $42^\circ$. The refractive index of the glass is approximately:

  1. $1.33$
  2. $1.41$
  3. $1.49$
  4. $2.42$
Show answer and solution

Correct answer: C. $1.49$

For total internal reflection at a denser-to-rarer interface, $\mu = \dfrac{1}{\sin C}$. With $C = 42^\circ$, $\sin 42^\circ \approx 0.669$, so $\mu = 1/0.669 \approx 1.49$, which matches typical crown glass. **Option A is water and option D is diamond.**

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A pendulum of mass m swings to amplitude angle θ. At the lowest point of swing, the TENSION in the string equals:

  1. mg
  2. mg(2 − cos θ)
  3. mg(3 − 2cos θ)
  4. 2mg sin θ
Show answer and solution

Correct answer: C. mg(3 − 2cos θ)

**At the lowest point:** T − mg = mv²/L (centripetal). v² at bottom = 2gL(1 − cos θ) (energy conservation from amplitude). We have So T = mg + 2mg(1 − cos θ). So So T = mg(3 − 2cos θ). For θ = 60°: T = mg(3 − 1) = 2mg.

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A car of mass 1000 kg moving at 36 km/h is stopped by brakes in 5 seconds. Average force exerted by brakes:

  1. 1000 N
  2. 2000 N
  3. 5000 N
  4. 10000 N
Show answer and solution

Correct answer: B. 2000 N

**Convert:** 36 km/h = 10 m/s. Deceleration a = (0 - 10)/5 = -2 m/s². Braking force F = ma = 1000 × 2 = 2000 N.

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