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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
Which has more power, a thick concave lens or a thin convex lens, made of the same glass? Give reason for your choice. |
| Answer» Thick convex lens, It has shorter focal length. | |
| 52. |
Where should an object be placed in front of a convex lens to get a real to get real image of the size of the object ?A. at the focus of the lensB. at twice the focal lengthC. at infinityD. between the optical center of lens and its focus. |
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Answer» Correct Answer - b At twice the focal length. |
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| 53. |
The ratio of sine of angle of incidence to the sine of angle of refraction. |
| Answer» Refractive index. | |
| 54. |
The wavelength of violet light is _____________ . |
| Answer» The wavelength of violet light is `ul(" 400 nm ")` . | |
| 55. |
Light from a sodium lamp `(lambda_0=589 nm)` passes through a tank of glycerin (refractive index `=1.47`) `20m` long in a time `t_1.` If it takes a time `t_2` to transverse the same tank when filled with carbon disulfide (index`=1.63`), determine the difference `t_2-t_1.` |
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Answer» Correct Answer - A `t_1=l/v_1=l/(c//mu_1)=(mu_1l)/e rArr t_2=(mu_2l)/c` `:. t_2-t_1=(mu_2-mu_1)l/c` `=((1.63-1.47)(20))/(3xx10^8)` `=1.07xx10^-8 s` |
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| 56. |
A light beam of wavelength `600nm` in air passes through film `1(n_1=1.2)` of thickness `1.0 mu m`,then through film `2`(air) of thickness `1.5mu m`, and finally through film `3(n_3=1.8)` of `thickness `1.0mu m`. (a) Which film does the light cross in the least time, and what is that least time? (b) What are the total number of wavelength (at any instant) across all three films together? |
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Answer» Correct Answer - A::B::D (a) `t_1=l/v_1=l/(c//n_1)=(n_1l)/c="minimum"` `=(1.2xx10^-6)/(3xx10^8)` `=4xx10^-15s` (b) `lambda=(lambda_0)/n` Number of wavelength across any film, `N=l/lambda=(ln)/(lambda_0)` |
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| 57. |
The refractive index of glass with respect to air is `3/2` and the refraction index of water with respect to air is `4/3`. The refractive index of glass with respect to water will be:A. `1.525`B. `1,225`C. `1.425`D. `1.125` |
| Answer» i) Crown glass to water ii) Water to diamond | |
| 58. |
The wavelength of ___________ light is the least which is ____________ . |
| Answer» The wavelength of `ul("violet")` light is the least which is `ul("400 nm")` . | |
| 59. |
1 nm = ___________ m. |
| Answer» 1 nm = `ul(10^(-9))` m. | |
| 60. |
The refractive index of water is 1.33. What will be the speed of light in waterA. 1.33B. 1.5C. 2.42D. 1.36 |
| Answer» Correct Answer - a) | |
| 61. |
Find the odd one out:Brown, blue,green, red |
| Answer» Brown. It is not a component of white light. Blue, red and green are components of while light. | |
| 62. |
Refractive index of water : 1.33 :: Refractive index of air : …………………. |
| Answer» 1.0003 : The value of refractive index is different for different media. | |
| 63. |
Least deviation : Red : : Maximum deviation : ……………… |
| Answer» Violet : The wavelength of violet is the smallest and therefore it deviates the maximum. | |
| 64. |
Diamond : Denser medium : : Air : …………….. |
| Answer» Rarer medium : The speed of light is more in air than in diamond. | |
| 65. |
Stars : Point source of light : : Plants : ……………… |
| Answer» Collection of point sources of light : Planets are much closer to us as compared to stars, therefore, they appear as a collection of point sources. | |
| 66. |
a) State and explain the laws of refraction of light with the help of a labelled diagram. b) What is meant by the refractive index of a substance? c) Light travels through air at 300 million `ms^(-1)`. On entering water it slows down to 225 million `ms^(-1)`. Calculate the refractive index of water. |
| Answer» `1.24 xx 10^(8)ms^(-1)` | |
| 67. |
When light of wavelength `lambda` on an equilateral prism, kept on its minimum deviation position, it is found that the angle of deviation equals the angle the angle of the prism itself. The refractive index of the material of the prism for the wavelength `lambda` isA. `sqrt3`B. `sqrt(3//2)`C. `2`D. `sqrt2` |
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Answer» Correct Answer - A ` A=delta_m=60^@ rArr mu=((sin(A+delta_m)/2))/sin(A//2)` |
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| 68. |
Lens : Transparent : : Mirror : ………………….. |
| Answer» Opaque : Light can pass through the lens whereas in a mirror, light cannot pass through because it is covered by a mirror coasting on the side. | |
| 69. |
Write the ratio of velocity of light in first medium to the velocity of light in the second medium. |
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Answer» Refractive index `=("Velocity of light in the first medium")/("Velocity of light in the second medium")` `therefore " "_(2)n_(1)=(v_(1))/(v_(2))` |
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| 70. |
The refractive index of four materials A,B,C and D are 1.3, 1.43, 1.71 and 1.52 respectively. When the light rays pass from air into these materials, they refract the minimum in:A. material AB. material BC. material CD. material D |
| Answer» Correct Answer - c) | |
| 71. |
The refractive indexes of four substances P,Q,R and S are 1.77, 1.52, 1.65 and 1.36 respectively. When light travelling in air is incident on these substances at equal angles, the angle of refraction will be the maximum in:A. in medium AB. in medium BC. in medium CD. in medium D |
| Answer» Correct Answer - c) | |
| 72. |
The refractive indices of four substances P,Q,R and S are 1.50, 1.36, 1.77 and 1.31 respectively. The speed of light is maximum in the substance:A. PB. QC. RD. S |
| Answer» Correct Answer - d) | |
| 73. |
If the speed of light in a medium is `1.5xx10^(8)m//s`, what is the absolute refractive index of the medium ? |
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Answer» Given : `V_(m)=1.5xx10^(8)m//s` `v_("vac")=3xx10^(8)m//s` To find : ` " "_(m)n_("vac")=` ? Formula : `" "_(m)n_("vac") =(V_(v))/(V_(m))` Solution : `" "_(m)n_("vac")=(3xx10^(8))/(1.5xx10^(8))` `" "_(m)n_("vac")=2` Absolute refractive index of the medium is 2. |
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| 74. |
A ray of light travelling in water falls at right angles to the boundary of a parallel-sided glass block. The ray of light:A. is refracted towards the normalB. is refracted away from the normalC. does not get refractedD. is reflected along the same path. |
| Answer» Correct Answer - c) | |
| 75. |
Light rays when travelling obliquely from Benzene to Air bend …………………. . |
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Answer» Light rays when travelling obliquely from Benzene to Air, bend `ul("away from the normal")`. Generally, when light rays travel obliquely from denser medium to rarer medium, it bends away from the normal as the velocity increase after entering air. Benzene is a denser medium, while air is the rarer medium. Velocity of light in benzene is less than that in air. |
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| 76. |
The speed of light in air is:A. `3 xx 10^(8) cm//s`B. `3 xx 10^(8) mm//s`C. `3 xx 10^(8)km//s`D. `3 xx 10^(8) m//s` |
| Answer» Correct Answer - d) | |
| 77. |
If the refractive index for light going from air to diamond be 2.42, what will bethe refractive index for light going from diamond to air? |
| Answer» Correct Answer - `0.41` | |
| 78. |
What is partial reflection ? |
| Answer» When light enters a rarer medium from denser medium, a part of it gets reflected and comes back into the denser medium as per laws of reflection. This is called partial reflection. | |
| 79. |
Light enters from air into diamond which has a refractive index of `2.42`. Calculate the speed of light in diamond. The speed of light in air is `3.0 xx 10^(8) ms^(-1)`. |
| Answer» `1.24 xx 10^(8)ms^(-1)` | |
| 80. |
A ray of light travelling in air goes into water. The angle of refraction will be:A. `90^(@)`B. smaller than the angle of incidenceC. equal to the angle of incidenceD. greater than the angle of incidence. |
| Answer» b) Refraction of light (as it comes out from water into air). | |
| 81. |
When a ray of light travelling in glass enters into water obliquely:A. it is refracted towards the normalB. it is not refracted at allC. it goes along the normalD. it is refracted away from the normal |
| Answer» Correct Answer - d) | |
| 82. |
In the figure shown `sin i/sin r` is equal to A. `(mu_2^2)/(mu_3mu_1)`B. `mu_3/mu_1`C. `(mu_3mu_1)/(mu_2^2)`D. `mu_1/mu_3` |
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Answer» Correct Answer - B `mu_1sini_1=mu_3sini_3` `:. mu_1sini=mu_3sinr` or `sini/sinr=mu_3/mu_1` |
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| 83. |
What is the value of angle of refraction if angle of incidence is `0^(@)` ? |
| Answer» If the angle of incidence is zero, then the angle of refraction is also zero. | |
| 84. |
When light enters from air to water, then itsA. frequency increases and speed decreasesB. frequency is same but the wavelength is smaller in water than in airC. frequency is same but the wavelength in water is greater than in airD. frequency decreases and wavelength is smaller in water than in air |
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Answer» Correct Answer - B Frequency does not change during refraction, but wavelength and speed decrease in a denser (here water) medium. |
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| 85. |
What is total internal reflection ? |
| Answer» When the angel of incidence in a denser medium is more than its critical angle, then the light reflects back into the denser medium. This is called total internal reflection. | |
| 86. |
A ray of light passes from glass into air. The angle of refraction will be:A. equal to the angle of incidence.B. greater than the angle of incidence.C. smaller than the angle of incidence.D. `45^(@)` |
| Answer» Correct Answer - d) | |
| 87. |
When sunlight passes through glass prism which light deviates the least ? |
| Answer» When sunlight passes through glass prism, the red light deviates the least. | |
| 88. |
Light is travelling from a denser medium to a rarer medim along a normal to the boundary:A. is refracted towards the normalB. is refracted away from the normalC. goes along the boundaryD. is not refracted |
| Answer» Correct Answer - d) | |
| 89. |
TRUE or FALSE:When light ray travels from denser medium to rarer medium, it travels parallel to the normal. |
| Answer» Light ray bends away from the normal. | |
| 90. |
What is the angle of incidence called, when angle of refraction is `90^(@)` ? |
| Answer» The angle of incidence is called as Critical angle. | |
| 91. |
TRUE or FALSE:If angle of incidence is zero, then the angle of refraction is `90^(@)`. |
| Answer» The angle of refraction would also be zero. | |
| 92. |
The following table gives the refractive indices of a few media: Use this table to give an example of: i)a medium pair so that light speeds up when it goes from one of these medium to another. ii) a medium pair so that lights slows down the when it goes from one of these medium to another. |
| Answer» Correct Answer - i) A ii) D | |
| 93. |
The refractive index depends on the ………………….. of light. |
| Answer» The refractive index depends upon the `ul("relative speed of propagation") ` of light in different media. This is because light has different velocities in different media. | |
| 94. |
Will light travel through a glass slab with the same velocity as it travels in air ? |
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Answer» (i) Refractive index depends on the velocity of light. (ii) As refractive index increases, velocity of light decreases. (iii) Since refractive index of glass is greater than air, the velocity of light in glass is lesser than that in air. |
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| 95. |
Will the velocity of light be same in all media ? |
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Answer» (i) Refractive index depends on the velocity of light. (ii) Refractive index is different for different media. (iii) Velocity of light will also be different for different media. |
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| 96. |
Why Red colour is used in danger signal? |
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Answer» (i) In a visible light range, the wavelength of red light is maximum, i.e. 700 nm. (ii) The maximum scattering of light is for blue light and the least scattering of red light takes place. (iii) Thus, red light can travel to longer distance and can be visible from far off distance. (iv) Therefore, the danger signals are red coloured. |
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| 97. |
It is possible to enjoy a rainbow at fountain in any season. |
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Answer» (i) The phenomenon of rainbow is a combined effect of dispersion, internal reflection and refraction. (ii) The rainbow appears in the sky after a rainfall. (iii) The water droplets of a fountain also act as small prisms as the rain drops. (iv) When the light rays enter these droplets, it first gets dispersed, then internally reflected and then refracted while coming out of the droplets. All these three processes together produce the rainbow. |
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| 98. |
Maximum refractive index : Violet : : Minimum refractive index : ………………….. |
| Answer» Red : Red light has the maximum wavelength and its refractive index is minimum compared to violet light which has the smallest wavelength. | |
| 99. |
`" "_(2)n_(1)=(v_(1))/(v_(2)): :""_(1)n_(2):` ……………….. |
| Answer» `(v_(2))/(v_(1))` : Velocity of light in a medium depends on the refractive index of the medium. | |
| 100. |
The refractive index of glass for light going from air to glass is `3/2`. The refractive index for light going from glass to air will be:A. `1/3`B. `4/5`C. `2/3`D. `5/2` |
| Answer» Correct Answer - c) | |