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<p style="color:blue;"><strong>Q1.</strong> Which three lie in the same plane according to first law of refraction?</p>
<p style="color:black;">a) Incident ray, reflected ray, mirror<br>
b) Incident ray, refracted ray, normal<br>
c) Normal, mirror, image<br>
d) Refracted ray, lens, axis</p>
<p style="color:green;"><strong>Answer:</strong> Incident ray, refracted ray, normal.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> The incident ray, refracted ray, and normal all lie in the same plane as per the first law of refraction.</p>
<p style="color:red;"><strong>Why others wrong:</strong> (a) reflected ray involves reflection; (c) image doesn’t define plane; (d) lens and axis unrelated.</p>
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<p style="color:blue;"><strong>Q2.</strong> The constant ratio in refraction law is between</p>
<p style="color:black;">a) angle of incidence and normal<br>
b) sine of angle of incidence and sine of refraction<br>
c) speed and wavelength<br>
d) angle of refraction and glass thickness</p>
<p style="color:green;"><strong>Answer:</strong> sine of angle of incidence and sine of refraction.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Snell’s law defines this ratio as constant for a given color in two media.</p>
<p style="color:red;"><strong>Why others wrong:</strong> (a) angles with normal not constant; (c) speed/wavelength is not constant; (d) angle/thickness irrelevant.</p>
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<p style="color:blue;"><strong>Q3.</strong> The law relating sine of angles is called</p>
<p style="color:black;">a) Newton’s law<br>
b) Fresnel law<br>
c) Snell’s law<br>
d) Einstein’s law</p>
<p style="color:green;"><strong>Answer:</strong> Snell’s law.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Snell’s law relates sine of incidence and refraction.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Newton, Fresnel, and Einstein did not define this law.</p>
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<p style="color:blue;"><strong>Q4.</strong> Refractive index is defined as</p>
<p style="color:black;">a) bending of light<br>
b) ratio of speeds of light<br>
c) reflection angle<br>
d) color shift of light</p>
<p style="color:green;"><strong>Answer:</strong> ratio of speeds of light.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Refractive index = speed in vacuum ÷ speed in medium.</p>
<p style="color:red;"><strong>Why others wrong:</strong> (a) bending is effect; (c, d) unrelated.</p>
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<p style="color:blue;"><strong>Q5.</strong> Symbol used for refractive index of medium 2 relative to medium 1 is</p>
<p style="color:black;">a) n12<br>
b) n21<br>
c) nm<br>
d) R</p>
<p style="color:green;"><strong>Answer:</strong> n21.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> n21 represents refractive index of medium 2 w.r.t 1.</p>
<p style="color:red;"><strong>Why others wrong:</strong> (a) reversed; (c, d) irrelevant symbols.</p>
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<p style="color:blue;"><strong>Q6.</strong> Refractive index represents change in</p>
<p style="color:black;">a) wavelength<br>
b) direction of light<br>
c) speed of light<br>
d) brightness</p>
<p style="color:green;"><strong>Answer:</strong> speed of light.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Light slows down when entering a medium, defining refractive index.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Wavelength and direction change are effects; brightness unaffected.</p>
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<p style="color:blue;"><strong>Q7.</strong> Light travels fastest in</p>
<p style="color:black;">a) water<br>
b) glass<br>
c) vacuum<br>
d) oil</p>
<p style="color:green;"><strong>Answer:</strong> vacuum.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Vacuum has no medium to slow light.</p>
<p style="color:red;"><strong>Why others wrong:</strong> All media slow light compared to vacuum.</p>
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<p style="color:blue;"><strong>Q8.</strong> Speed of light in vacuum is</p>
<p style="color:black;">a) 3×10⁶ m/s<br>
b) 3×10⁷ m/s<br>
c) 3×10⁸ m/s<br>
d) 3×10⁹ m/s</p>
<p style="color:green;"><strong>Answer:</strong> 3×10⁸ m/s.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Standard speed of light in vacuum.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Others are off by factors of 10.</p>
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<p style="color:blue;"><strong>Q9.</strong> Speed of light in air compared to vacuum is</p>
<p style="color:black;">a) much more<br>
b) same<br>
c) marginally less<br>
d) zero</p>
<p style="color:green;"><strong>Answer:</strong> marginally less.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Air slightly slows light compared to vacuum.</p>
<p style="color:red;"><strong>Why others wrong:</strong> (a) impossible; (b) not exactly same; (d) zero false.</p>
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<p style="color:blue;"><strong>Q10.</strong> Speed of light in water is</p>
<p style="color:black;">a) same as vacuum<br>
b) slightly more<br>
c) considerably less<br>
d) infinite</p>
<p style="color:green;"><strong>Answer:</strong> considerably less.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Water slows light more than air.</p>
<p style="color:red;"><strong>Why others wrong:</strong> (a, b) false; (d) impossible.</p>
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<p style="color:blue;"><strong>Q11.</strong> If light goes from medium 1 to 2, refractive index is</p>
<p style="color:black;">a) v2/v1<br>
b) v1/v2<br>
c) v1+v2<br>
d) v2−v1</p>
<p style="color:green;"><strong>Answer:</strong> v1/v2.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Refractive index = speed in first medium ÷ speed in second medium.</p>
<p style="color:red;"><strong>Why others wrong:</strong> (a) reversed; (c, d) sums/differences irrelevant.</p>
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<p style="color:blue;"><strong>Q12.</strong> Refractive index depends on</p>
<p style="color:black;">a) shape<br>
b) color<br>
c) speed in medium<br>
d) size</p>
<p style="color:green;"><strong>Answer:</strong> speed in medium.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Refractive index is based on light speed in the medium.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Shape, color, size don’t determine index directly.</p>
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<p style="color:blue;"><strong>Q13.</strong> Angle of incidence is represented by</p>
<p style="color:black;">a) r<br>
b) i<br>
c) n<br>
d) v</p>
<p style="color:green;"><strong>Answer:</strong> i.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Standard notation for angle of incidence.</p>
<p style="color:red;"><strong>Why others wrong:</strong> (a) refraction; (c) refractive index; (d) velocity.</p>
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<p style="color:blue;"><strong>Q14.</strong> Angle of refraction is denoted by</p>
<p style="color:black;">a) r<br>
b) i<br>
c) n<br>
d) c</p>
<p style="color:green;"><strong>Answer:</strong> r.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Standard symbol for angle of refraction.</p>
<p style="color:red;"><strong>Why others wrong:</strong> (b) incidence; (c) refractive index; (d) speed of light.</p>
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<p style="color:blue;"><strong>Q15.</strong> Refractive index of water is</p>
<p style="color:black;">a) 1.00<br>
b) 1.25<br>
c) 1.33<br>
d) 1.50</p>
<p style="color:green;"><strong>Answer:</strong> 1.33.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Standard value for water.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Other values are incorrect.</p>
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<p style="color:blue;"><strong>Q16.</strong> Refractive index indicates</p>
<p style="color:black;">a) mass density<br>
b) optical density<br>
c) thickness<br>
d) brightness</p>
<p style="color:green;"><strong>Answer:</strong> optical density.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Refractive index measures optical “heaviness” of medium.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Mass, thickness, brightness unrelated.</p>
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<p style="color:blue;"><strong>Q17.</strong> When light enters another medium obliquely, it</p>
<p style="color:black;">a) stops<br>
b) bends<br>
c) reflects<br>
d) vanishes</p>
<p style="color:green;"><strong>Answer:</strong> bends.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Oblique incidence causes change in direction (refraction).</p>
<p style="color:red;"><strong>Why others wrong:</strong> (a, d) false; (c) reflection only occurs partially.</p>
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<p style="color:blue;"><strong>Q18.</strong> Refractive index of medium 1 w.r.t 2 is</p>
<p style="color:black;">a) n21<br>
b) n12<br>
c) nm<br>
d) R</p>
<p style="color:green;"><strong>Answer:</strong> n12.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> n12 denotes medium 1 relative to 2.</p>
<p style="color:red;"><strong>Why others wrong:</strong> (a) reversed; (c, d) irrelevant symbols.</p>
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<p style="color:blue;"><strong>Q19.</strong> Absolute refractive index is taken with respect to</p>
<p style="color:black;">a) water<br>
b) glass<br>
c) air/vacuum<br>
d) oil</p>
<p style="color:green;"><strong>Answer:</strong> air/vacuum.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Absolute index = speed in vacuum ÷ speed in medium.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Other media give relative indices.</p>
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<p style="color:blue;"><strong>Q20.</strong> Symbol for absolute refractive index is</p>
<p style="color:black;">a) n21<br>
b) nm<br>
c) n12<br>
d) r</p>
<p style="color:green;"><strong>Answer:</strong> nm.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> nm denotes absolute refractive index.</p>
<p style="color:red;"><strong>Why others wrong:</strong> n12/n21 are relative; r is angle.</p>
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<p style="color:blue;"><strong>Q21.</strong> Formula for absolute refractive index is</p>
<p style="color:black;">a) v/c<br>
b) c/v<br>
c) v1/v2<br>
d) v2/v1</p>
<p style="color:green;"><strong>Answer:</strong> c/v.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Absolute index = speed in vacuum ÷ speed in medium.</p>
<p style="color:red;"><strong>Why others wrong:</strong> (a) reversed; (c, d) formulas for relative index.</p>
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<p style="color:blue;"><strong>Q22.</strong> Refraction occurs due to change in</p>
<p style="color:black;">a) direction only<br>
b) wavelength only<br>
c) speed only<br>
d) speed and direction</p>
<p style="color:green;"><strong>Answer:</strong> speed and direction.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Both speed and bending occur during refraction.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Single factor alone is incomplete.</p>
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<p style="color:blue;"><strong>Q23.</strong> Refractive index is a</p>
<p style="color:black;">a) vector<br>
b) scalar<br>
c) force<br>
d) energy</p>
<p style="color:green;"><strong>Answer:</strong> scalar.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Magnitude only, no direction.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Not vector, force, or energy.</p>
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<p style="color:blue;"><strong>Q24.</strong> Snell’s law is valid for</p>
<p style="color:black;">a) given color & media<br>
b) all colors equally<br>
c) vacuum only<br>
d) water only</p>
<p style="color:green;"><strong>Answer:</strong> given color & media.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Dispersion causes slight variation with color.</p>
<p style="color:red;"><strong>Why others wrong:</strong> (b) not exact; (c, d) too specific.</p>
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<p style="color:blue;"><strong>Q25.</strong> Refractive index changes when</p>
<p style="color:black;">a) medium changes<br>
b) object moves<br>
c) angle changes<br>
d) thickness changes</p>
<p style="color:green;"><strong>Answer:</strong> medium changes.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Different media have different optical densities.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Angle, thickness, motion irrelevant.</p>
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<p style="color:blue;"><strong>Q26.</strong> Normal is drawn</p>
<p style="color:black;">a) parallel<br>
b) perpendicular<br>
c) slanted<br>
d) curved</p>
<p style="color:green;"><strong>Answer:</strong> perpendicular.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Normal is always perpendicular to surface at point of incidence.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Other orientations incorrect.</p>
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<p style="color:blue;"><strong>Q27.</strong> No refraction when incidence is</p>
<p style="color:black;">a) oblique<br>
b) large<br>
c) normal<br>
d) small</p>
<p style="color:green;"><strong>Answer:</strong> normal.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Light enters straight, no bending.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Oblique incidence causes bending.</p>
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<p style="color:blue;"><strong>Q28.</strong> sin i / sin r is</p>
<p style="color:black;">a) random<br>
b) constant<br>
c) zero<br>
d) infinite</p>
<p style="color:green;"><strong>Answer:</strong> constant.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Snell’s law defines constant ratio.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Not random, zero, or infinite.</p>
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<p style="color:blue;"><strong>Q29.</strong> Refraction proves light changes</p>
<p style="color:black;">a) color<br>
b) speed<br>
c) shape<br>
d) size</p>
<p style="color:green;"><strong>Answer:</strong> speed.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Light slows in denser medium.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Refraction doesn’t change color, shape, or size.</p>
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<p style="color:blue;"><strong>Q30.</strong> Higher refractive index indicates</p>
<p style="color:black;">a) higher speed<br>
b) lower speed<br>
c) same speed<br>
d) random speed</p>
<p style="color:green;"><strong>Answer:</strong> lower speed.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Higher index means slower light in medium.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Higher, same, or random speeds false.</p>
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<p style="color:blue;"><strong>Q31.</strong> When light slows, refractive index</p>
<p style="color:black;">a) falls<br>
b) rises<br>
c) vanishes<br>
d) reverses</p>
<p style="color:green;"><strong>Answer:</strong> rises.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Slower light → higher refractive index.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Falling, vanishing, reversing false.</p>
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<p style="color:blue;"><strong>Q32.</strong> Refraction happens at</p>
<p style="color:black;">a) center<br>
b) mirror<br>
c) boundary<br>
d) source</p>
<p style="color:green;"><strong>Answer:</strong> boundary.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Occurs at interface between two media.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Not at center, mirror, or source.</p>
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<p style="color:blue;"><strong>Q33.</strong> Refractive index of vacuum is</p>
<p style="color:black;">a) 0<br>
b) 1<br>
c) 1.33<br>
d) infinity</p>
<p style="color:green;"><strong>Answer:</strong> 1.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> By definition, speed in vacuum ÷ speed in vacuum = 1.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Other values incorrect.</p>
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<p style="color:blue;"><strong>Q34.</strong> Glass has higher refractive index than</p>
<p style="color:black;">a) air<br>
b) diamond<br>
c) water<br>
d) plastic</p>
<p style="color:green;"><strong>Answer:</strong> air.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Glass is denser optically than air.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Diamond > glass; water/plastic < glass.</p>
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<p style="color:blue;"><strong>Q35.</strong> Snell’s law relates</p>
<p style="color:black;">a) angles<br>
b) sines<br>
c) speeds<br>
d) distances</p>
<p style="color:green;"><strong>Answer:</strong> sines.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Ratio of sines of angles is constant.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Not angles, speeds, or distances directly.</p>
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<p style="color:blue;"><strong>Q36.</strong> Refraction occurs in</p>
<p style="color:black;">a) mirrors<br>
b) transparent media<br>
c) metals<br>
d) vacuum only</p>
<p style="color:green;"><strong>Answer:</strong> transparent media.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Light bends when entering a different transparent medium.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Mirrors reflect; metals absorb; vacuum has no refraction.</p>
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<p style="color:blue;"><strong>Q37.</strong> Maximum slowing of light occurs in</p>
<p style="color:black;">a) air<br>
b) water<br>
c) glass<br>
d) vacuum</p>
<p style="color:green;"><strong>Answer:</strong> glass.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Denser medium slows light most.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Air slower than vacuum; water slower than air; vacuum fastest.</p>
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<p style="color:blue;"><strong>Q38.</strong> Symbol for refractive index</p>
<p style="color:black;">a) f<br>
b) m<br>
c) n<br>
d) R</p>
<p style="color:green;"><strong>Answer:</strong> n.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Standard symbol.</p>
<p style="color:red;"><strong>Why others wrong:</strong> f, m, R incorrect.</p>
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<p style="color:blue;"><strong>Q39.</strong> Refractive index increases when speed</p>
<p style="color:black;">a) increases<br>
b) decreases<br>
c) same<br>
d) random</p>
<p style="color:green;"><strong>Answer:</strong> decreases.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Slower light → higher index.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Faster, same, random incorrect.</p>
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<p style="color:blue;"><strong>Q40.</strong> Refractive index depends on color because of</p>
<p style="color:black;">a) reflection<br>
b) dispersion<br>
c) absorption<br>
d) expansion</p>
<p style="color:green;"><strong>Answer:</strong> dispersion.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Different wavelengths refract differently.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Reflection, absorption, expansion not responsible.</p>
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<p style="color:blue;"><strong>Q41.</strong> Law of refraction states ratio is constant for</p>
<p style="color:black;">a) all light<br>
b) white light only<br>
c) given color<br>
d) night light</p>
<p style="color:green;"><strong>Answer:</strong> given color.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Snell’s law applies to specific wavelength.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Other colors vary slightly; night light irrelevant.</p>
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<p style="color:blue;"><strong>Q42.</strong> Refractive index compares speed in</p>
<p style="color:black;">a) two media<br>
b) two mirrors<br>
c) same medium<br>
d) vacuum only</p>
<p style="color:green;"><strong>Answer:</strong> two media.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Ratio = speed in first medium ÷ second medium.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Mirrors, same medium, vacuum only incorrect.</p>
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<p style="color:blue;"><strong>Q43.</strong> If medium 2 is denser, refracted ray bends</p>
<p style="color:black;">a) towards normal<br>
b) away from normal<br>
c) straight<br>
d) back</p>
<p style="color:green;"><strong>Answer:</strong> towards normal.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Light slows in denser medium, bends toward normal.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Away, straight, or back false.</p>
<hr style="border:1px solid gray;">
<p style="color:blue;"><strong>Q44.</strong> Absolute refractive index compares medium with</p>
<p style="color:black;">a) water<br>
b) glass<br>
c) air/vacuum<br>
d) oil</p>
<p style="color:green;"><strong>Answer:</strong> air/vacuum.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Absolute index always w.r.t vacuum.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Others give relative indices.</p>
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<p style="color:blue;"><strong>Q45.</strong> Refractive index unit is</p>
<p style="color:black;">a) m/s<br>
b) meter<br>
c) none<br>
d) second</p>
<p style="color:green;"><strong>Answer:</strong> none.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Refractive index is dimensionless.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Not a physical unit.</p>
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<p style="color:blue;"><strong>Q46.</strong> Smaller wavelength means</p>
<p style="color:black;">a) lower refractive index<br>
b) higher refractive index<br>
c) no effect<br>
d) infinite index</p>
<p style="color:green;"><strong>Answer:</strong> higher refractive index.</p>
<p style="color:darkorange;"><strong>Why correct
<p style="color:blue;"><strong>Q46.</strong> Smaller wavelength means</p>
<p style="color:black;">a) lower refractive index<br>
b) higher refractive index<br>
c) no effect<br>
d) infinite index</p>
<p style="color:green;"><strong>Answer:</strong> higher refractive index.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Due to dispersion, shorter wavelengths (smaller λ) are refracted more and typically experience a higher refractive index.</p>
<p style="color:red;"><strong>Why others wrong:</strong> (a) shorter wavelength does not lower the index; (c) there is an effect (dispersion); (d) infinite index is meaningless here.</p>
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<p style="color:blue;"><strong>Q47.</strong> Light entering denser medium becomes</p>
<p style="color:black;">a) faster<br>
b) slower<br>
c) same<br>
d) zero</p>
<p style="color:green;"><strong>Answer:</strong> slower.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> In a denser optical medium the speed of light decreases, giving a higher refractive index.</p>
<p style="color:red;"><strong>Why others wrong:</strong> (a) opposite of correct; (c) speed changes when medium changes; (d) cannot become zero.</p>
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<p style="color:blue;"><strong>Q48.</strong> Refraction shows light does not travel</p>
<p style="color:black;">a) in vacuum<br>
b) in air only<br>
c) same in all<br>
d) in lanes</p>
<p style="color:green;"><strong>Answer:</strong> same in all.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Refraction demonstrates that light's speed varies with the medium, so it does not travel the same speed in all media.</p>
<p style="color:red;"><strong>Why others wrong:</strong> (a) light does travel in vacuum; (b) it travels in many media, not only air; (d) "lanes" is meaningless.</p>
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<p style="color:blue;"><strong>Q49.</strong> Medium with lowest refractive index is</p>
<p style="color:black;">a) glass<br>
b) water<br>
c) air<br>
d) diamond</p>
<p style="color:green;"><strong>Answer:</strong> air.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Among the listed media, air has the refractive index closest to 1, the lowest optical density.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Glass, water, and diamond are optically denser and have higher refractive indices.</p>
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<p style="color:blue;"><strong>Q50.</strong> Highest refractive index among given is</p>
<p style="color:black;">a) air<br>
b) water<br>
c) glass<br>
d) diamond</p>
<p style="color:green;"><strong>Answer:</strong> diamond.</p>
<p style="color:darkorange;"><strong>Why correct:</strong> Diamond has a very high refractive index (≈2.42), higher than air, water, or typical glass.</p>
<p style="color:red;"><strong>Why others wrong:</strong> Air, water, and glass have significantly lower refractive indices than diamond.</p>
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