Question 1 of 10 Critical angle of light passing from glass to air is minimum for A red B green C yellow D d. violet 💡 Explanation Critical angle is given by [latex]\sin C = \dfrac{1}{n}[/latex]. Since violet light has the highest refractive index among visible colors (due to greater dispersion at higher frequencies), it has the smallest [latex]\sin C[/latex] and thus the minimum critical angle. Question 2 of 10 The index of refraction of diamond is 2.4, velocity of light in diamond is A [latex]1.25 \times 10^8\ ms^{-1}[/latex] B [latex]2.5 \times 10^8\ ms^{-1}[/latex] C [latex]1.5 \times 10^8\ ms^{-1}[/latex] D [latex]2.0 \times 10^8\ ms^{-1}[/latex] 💡 Explanation Using [latex]\mu = \dfrac{c}{v}[/latex], [latex]v = \dfrac{c}{n} = \dfrac{3 \times 10^8}{2.4} = 1.25 \times 10^8,ms^{-1}[/latex]. Question 3 of 10 The refractive index of glass is 1.5. Then velocity of which light is minimum in the glass? A Violet B Red C Yellow D Green 💡 Explanation Since [latex]v = \dfrac{c}{\mu}[/latex], the color with the highest refractive index travels slowest. Violet light has the highest refractive index among visible colors (due to its shorter wavelength and greater dispersion), so it has the minimum velocity in glass. Question 4 of 10 The refractive index of glass is 1.5 and water is 1.33. Then what is the critical angle for glass water interface? A 54.6° B 48° C 62.73° D 56° 💡 Explanation For light going from glass (denser) to water (rarer), [latex]\sin C = \dfrac{\mu_{water}}{\mu_{glass}} = \dfrac{1.33}{1.5} = 0.8867[/latex], so [latex]C = \sin^{-1}(0.8867) \approx 62.73°[/latex]. Question 5 of 10 The refractive index [latex](\mu)[/latex] and wavelength of light [latex](\lambda)[/latex] when light passes from one medium to another medium A [latex]\mu \propto \lambda^{-1}[/latex] B [latex]\mu \propto \lambda^{-2}[/latex] C [latex]\mu \propto \lambda^{-3}[/latex] D [latex]\mu \propto \lambda^{-4}[/latex] 💡 Explanation This follows Cauchy's dispersion relation, [latex]\mu = A + \dfrac{B}{\lambda^2}[/latex], where the dominant variable term shows the refractive index varies approximately as the inverse square of the wavelength. Question 6 of 10 Refractive index of glass with respect to air is 1.5. What is the velocity of light in the material? A [latex]3 \times 10^8\ m/s[/latex] B [latex]2 \times 10^8\ m/s[/latex] C [latex]1.5 \times 10^8\ m/s[/latex] D [latex]4 \times 10^8\ m/s[/latex] 💡 Explanation Using [latex]\mu = \dfrac{c}{v}[/latex], [latex]v = \dfrac{c}{\mu} = \dfrac{3 \times 10^8}{1.5} = 2 \times 10^8,m/s[/latex]. Question 7 of 10 A person inside water can see the sun setting at an angle of A 41° B 60° C 90° D 49° 💡 Explanation When the sun is at the horizon, light rays from it graze the water surface at 90° (the maximum possible angle of incidence), and refract into water at the critical angle for water-air interface, which is approximately 49° (since [latex]\sin C = 1/1.33[/latex]). Question 8 of 10 Light from vacuum enters a medium of [latex]\mu = 1.5[/latex]. If it crosses the glass within a nanosecond, the thickness of the medium is A 10 cm B 20 cm C 40 cm D 70 cm 💡 Explanation Velocity in medium [latex]v = \dfrac{c}{\mu} = \dfrac{3 \times 10^8}{1.5} = 2 \times 10^8,m/s[/latex]. Thickness [latex]= v \times t = (2 \times 10^8)(10^{-9}) = 0.2,m = 20,cm[/latex]. Question 9 of 10 Optical fibres are based on the principle of A refraction B total internal reflection C dispersion D interference 💡 Explanation The physically correct principle behind optical fibres is total internal reflection Question 10 of 10 If refractive index of water is 4/3 and that of given slab of glass immersed in it is 5/3. What is the critical angle for a ray of light tending to go from glass to water? A [latex]\sin^{-1}(3/4)[/latex] B [latex]\sin^{-1}(3/5)[/latex] C [latex]\sin^{-1}(4/5)[/latex] D none 💡 Explanation For light going from glass (denser) to water (rarer), [latex]\sin C = \dfrac{\mu_{water}}{\mu_{glass}} = \dfrac{4/3}{5/3} = \dfrac{4}{5}[/latex], so [latex]C = \sin^{-1}(4/5)[/latex]. ← Prev Check Next → Finish & See Score 0 of 10 checked ← Back 1 / 10 1 2 3 4 5 6 7 8 9 10
