Ray Optics PYQs Set 7 (PDF)

Set 7 of 18 · Questions 181-210 of 521

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Mere Teacher · Previous Year Questions JEE Main Physics · Ray Optics · Set 7 (Q181-210)
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181. $A concave mirror for face viewing has focal length of 0.4 m The distance at which you hold the mirror from your face in order to see your image upright with a magnification of 5 is:$ (1) $0.24 m$ (2) $1.60 m$ (3) $0.32 m$ (4) $0.16 m$ 182. $A person is suffering from myopic defect. He is able to see clear objects placed at 15 cm. What type and of what focal length of lens he should use to see clearly the object placed 60 cm away$ (1) $Concave lens of 20 cm focal length$ (2) $Convex lens of 20 cm focal length$ (3) $Concave lens of 12 cm focal length$ (4) $Convex lens of 12 cm focal length$ 183. $Given below are two statements: one is labelled as Assertion (A)and the other is labelled as Reason (R).Assertion (A): Refractive index of glass is higher than that of air.Reason (R): Optical density of a medium is directly proportionate to its mass density which results in a proportionate refractive index.In the light of the above statements, choose the most appropriate answer from the options given below:$ (1) $Both (A)and (R) are correct and (R) is the correct explanation of (A)$ (2) $(A) is correct but (R) is not correct$ (3) $(A) is not correct but (R) is correct$ (4) $Both (A)and (R) are correct but (R) is not the correct explanation of (A)$ 184. $Focal length of a conver lens will be maximum for$ (1) $Green light$ (2) $Blue light$ (3) $Red light$ (4) $Yellow light$ 185. $If the scattering intensity of a liquid is 8 units at a wavelength of 500 nm, then the scattering intensity at a wavelength of 400 nm will be approximately$ (1) $13 units$ (2) $16 units$ (3) $20 units$ (4) $24 units$ 186. $An electromagnetic radiation of frequency , wavelength , travelling with velocity in air, enters a glass slab of refractive index . The frequency, wavelength and velocity oflight in the glass slab will be respectively$ (1) $n, 2 λ and \frac{v}{μ}$ (2) $\frac{2 n}{μ}, \frac{λ}{μ} and v$ (3) $\frac{n}{μ}, \frac{λ}{μ} and \frac{v}{μ}$ (4) $n, \frac{λ}{μ} and \frac{v}{μ}$ 187. $For a given pair of transparent media, the critical angle for which colour is maximum?$ (1) $Green$ (2) $Red$ (3) $Blue$ (4) $Violet$ 188. $A prism of certain angle deviates the red and blue rays by 8^{\circ} and 12^{\circ} respectively. Another prism of the same angle deviates the red and blue rays by 10^{\circ} and 14^{\circ} respectively. The prisms are small angled and made of different materials. The dispersive powers of the materials of the prisms are in the ratio$ (1) $5 : 6$ (2) $9 : 11$ (3) $6 : 5$ (4) $11 : 9$ 189. $The equiconvex lens has a focal length ' f'. If the lens is cut along the line perpendicular to principal axis and passing through the pole, what will be the focal length of any half part?$ (1) $\frac{f}{2}$ (2) $2 f$ (3) $\frac{3 f}{2}$ (4) $f$ 190. $Frequencies of light incident on a system of scattering particles are in the ratio of 1 : 2 . Then, the intensity of scattered light in a particular direction is ...$ (1) $1 : 4$ (2) $1 : 2$ (3) $1 : 8$ (4) $1 : 16$ 191. $The refracting angle of a prism is and refractive index of material of prism is . The angle of minimum deviation is$ (1) $90^{\circ} - A$ (2) $180^{\circ} - 2 A$ (3) $180^{\circ} - 3 A$ (4) $180^{\circ} + 2 A$ 192. $A thin convex lens of focal length made of crown glass is immersed in a liquid of refractive index , where is the refractive index of the crown glass. The convex lens now is$ (1) $a convex lens of longer focal length$ (2) $a convex lens of shorter focal length$ (3) $. a divergent lens$ (4) $a convex lens of focal length (μ_{c} - μ_{l}) f$ 193. $The blue colour of the sky is due to the phenomenon of$ (1) $scattering$ (2) $dispersion$ (3) $reflection$ (4) $refraction.$ 194. $Two particles move at right angle to each other. Their de Broglie wavelengths are λ_{1} and λ_{2} respectively. The particles suffer perfectly inelastic collision. The de Broglie wavelength λ of the final particle, is given by:$ (1) $\frac{1}{λ ^{2}} = \frac{1}{λ _{1}^{2}} + \frac{1}{λ _{2}^{2}}$ (2) $λ = λ_{1} λ_{2}$ (3) $λ = \frac{λ _{2} + λ _{2}}{2}$ (4) $\frac{2}{λ} = \frac{1}{λ _{1}} + \frac{1}{λ _{2}}$ 195. $A person wants a real image of his own, 3 times enlarged. Where should he stand infront of a concave mirror of radius of curvature 30 cm ?$ (1) $30 cm$ (2) $20 cm$ (3) $10 cm$ (4) $90 cm$ 196. $When an object is placed 40 cm away from a spherical mirror an image of magnification \frac{1}{2} is produced. To obtain an image with magnification of \frac{1}{3}, the object is to be moved:$ (1) $20 cm away from the mirror.$ (2) $20 cm towards the mirror.$ (3) $80 cm away from the mirror.$ (4) $40 cm away from the mirror.$ 197. $A satisfactory photographic print is obtained when the exposure time is 10 sec at a distance of 2 m from a 60 cd lamp. The time of exposure required for the same quality print at a distance of 4 m from a 120 cd lamp is$ (1) $5 sec$ (2) $10 sec$ (3) $15 sec$ (4) $20 sec$ 198. $5 The refractive index of the material of a glass prism is . The angle of minimumdeviation is equal to the angle of the prism. What is the angle of the prism?$ (1) $60^{\circ}$ (2) $58^{\circ}$ (3) $48^{\circ}$ (4) $50^{\circ}$ 199. $When the power of eye lens increases, the defect of vision is produced. The defect is known as$ (1) $Shortsightedness$ (2) $Long-sightedness$ (3) $Colorblindness$ (4) $None of the above$ 200. $The magnifications produced by a convex lens for two position of an object are 4 and 3, respectively. If the distance of separation between the two positions of the object is 2 cm, then the focal length of the lens is$ (1) $20 cm$ (2) $16 cm$ (3) $28 cm$ (4) $24 cm$ 201. $An effective power of a combination of 5 identical convex lenses which are kept in contact along the principal axis is 25 D. Focal length of each of the convex lens is :$ (1) $20 cm$ (2) $50 cm$ (3) $500 cm$ (4) $25 cm$ 202. $The focal length of a plano convex lens is and its refractive index is 1.5 . It is kept over a plane glass plate with its curved surface touching the glass plate. The gap between the lens and the glass plate is filled by a liquid. As a result, the effective focal length of the combination becomes . Then the refractive index of the liquid is$ (1) $1.5$ (2) $2$ (3) $1.25$ (4) $1.33$ 203. $In the diagram given below, there are three lenses formed. Considering negligible thickness of each of them as compared to (R_{1}) and (R_{2}), i.e., the radii of curvature for upper and lower surfaces of the glass lens, the power of the combination is$ (1) $\frac{1}{6} (\frac{1}{( R _{1} )} - \frac{1}{( R _{2} )})$ (2) $- \frac{1}{6} (\frac{1}{( R _{1} )} + \frac{1}{( R _{2} )})$ (3) $\frac{1}{6} (\frac{1}{( R _{1} )} + \frac{1}{( R _{2} )})$ (4) $- \frac{1}{6} (\frac{1}{( R _{1} )} - \frac{1}{( R _{2} )})$ 204. $A diverging lens with magnitude of focal length 25cm is placed at a distance of 15 cm from a converging lens of magnitude of focal length 20 cm. A beam of parallel light falls on the diverging lens. The final image formed is :$ (1) $real and at a distance of 6 cm from the convergent lens$ (2) $real and at a distance of 40 cm from convergent lens.$ (3) $virtual and at a distance of 40 cm from convergent lens$ (4) $real and at distance of 40 cm from the divergent lens.$ 205. $Two slits in Young’s experiment have widths in the ratio 1 : 25. The ratio of intensity at the maxima and minima in the interference pattern, is$ (1) $\frac{49}{121}$ (2) $\frac{4}{9}$ (3) $\frac{9}{4}$ (4) $\frac{121}{49} .$ 206. $The far point of a near sighted person is 6.0 m from her eyes, and she wears contacts that enable her to see distant objects clearly. A tree is 18.0 m away 2.0 m high. How high is the image formed by the contacts?$ (1) $0.1 m$ (2) $1.5 m$ (3) $0.75 m$ (4) $0.50 m$ 207. $A convex lens is put 10 cm from a light source and it makes a sharp image on a screen, kept 10 cm from the lens. Now a glass block (refractive index 1.5) of 1.5 cm thickness is placed in contact with the light source. To get the sharp image again,, the screen is shifted by a distance d. Then d is :$ (1) $1.1 cm away from the lens$ (2) $0.55 cm away from the lens$ (3) $0.55 cm towards the lens$ (4) $0$ 208. $A finite size object is placed normal to the principal axis at a distance of 30 cm from a convex mirror of focal length 30 cm. A plane mirror is now placed in such a way that the image produced by both the mirrors coincide with each other. The distance between the two mirrors is:$ (1) $45 cm$ (2) $15 cm$ (3) $22.5 cm$ (4) $7.5 cm$ 209. $The angle of incidence for a ray oflight at a refracting surface of a prism is . The angle of prism is . If the ray suffers minimum deviation through the prism, the angle of minimum deviation and refractive index ofthe material ofthe prism respectively, are$ (1) $4 5^{\circ}; 2$ (2) $3 0^{\circ}; \frac{1}{2}$ (3) $4 5^{\circ}; \frac{1}{2}$ (4) $3 0^{\circ}; 2 .$ 210. $A convex lens of focal length 20 cm is placed in front of convex mirror with principal axis coinciding each other. The distance between the lens and mirror is 10 cm. A point object is placed on principal axis at a distance of 60 cm from the convex lens. The image formed by combination coincides the object itself. The focal length of the convex mirror is _____cm.$