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OJEE Ray Optics and Optical Instruments — practice questions — page 2

Explore 78 free Ray Optics and Optical Instruments questions in OJEE Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Ray Optics and Optical Instruments questions and exercises with answers

Showing questions 31–60 of 78.

Speed of light in a medium of refractive index n:Read the answer and worked solution →Object at focus of a convex lens. Image is:Read the answer and worked solution →An object 4 cm tall is placed 30 cm in front of a concave mirror of focal length 20 cm. Image position and size:Read the answer and worked solution →For an apparent depth of swimming pool seen from above (real depth d, water n = 4/3):Read the answer and worked solution →Critical angle for diamond (n = 2.42):Read the answer and worked solution →Combination of two lenses, f₁ = 20 cm convex and f₂ = -25 cm concave, in contact. Equivalent power:Read the answer and worked solution →Dispersion of light by prism: angular dispersion (δ_violet - δ_red) for thin prism:Read the answer and worked solution →A coin at the bottom of a 0.5 m water tank (n = 4/3) appears at depth:Read the answer and worked solution →In Young's double slit experiment, fringe width:Read the answer and worked solution →Refractive index of medium 1 w.r.t. medium 2 is n₁₂. Then:Read the answer and worked solution →Magnifying power of simple magnifier (image at near point):Read the answer and worked solution →For object at 60 cm from convex lens of f = 20 cm, image is:Read the answer and worked solution →For total internal reflection at glass-water interface (n_g = 1.5, n_w = 1.33), critical angle:Read the answer and worked solution →A ray enters a glass slab at 45°. Glass n = 1.5. Angle of refraction inside glass:Read the answer and worked solution →Refraction — true or false?Read the answer and worked solution →Find the property that does not match concave mirrorsRead the answer and worked solution →Complete the lens formulaRead the answer and worked solution →Pick the higher optical valueRead the answer and worked solution →Sort microscope from telescopeRead the answer and worked solution →Key in the ray optics answersRead the answer and worked solution →Complete the lens power ruleRead the answer and worked solution →Sort reflection from refractionRead 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 →

Worked practice questions

Speed of light in a medium of refractive index n:

  1. n c
  2. c × n²
  3. c / n (light slows down in dense medium)
  4. c
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Correct answer: C. c / n (light slows down in dense medium)

v = c/n. Higher n → slower light. In water (n = 1.33): v ≈ 2.26 × 10⁸ m/s. In glass (n ≈ 1.5): v ≈ 2 × 10⁸ m/s. Refraction arises because of this speed change.

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Object at focus of a convex lens. Image is:

  1. At focus
  2. Between lens and focus
  3. At infinity (parallel rays)
  4. At 2f
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Correct answer: C. At infinity (parallel rays)

**Object at focal point:** rays emerge parallel after lens, image at infinity. Magnification infinite. Used in collimators and searchlights.

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An object 4 cm tall is placed 30 cm in front of a concave mirror of focal length 20 cm. Image position and size:

  1. v = 30 cm
  2. v = 12 cm
  3. v = 60 cm, h = 8 cm, inverted, real
  4. v = -60 cm
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Correct answer: C. v = 60 cm, h = 8 cm, inverted, real

1/v + 1/u = 1/f. Using u = -30 cm, f = -20 cm (concave): 1/v = 1/(-20) - 1/(-30) = -1/60 → v = -60 cm (in front of mirror, real). m = -v/u = -(-60)/(-30) = -2. Image height = -2 × 4 = -8 cm (inverted, 8 cm tall).

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