Ray Optics PYQs Set 14 (PDF)

Set 14 of 18 · Questions 391-420 of 521

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Mere Teacher · Previous Year Questions JEE Main Physics · Ray Optics · Set 14 (Q391-420)
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391. $An object is placed at a distance of 40 cm from a concave mirror of focal length 15 cm . If the object is displaced through a distance of 20 cm towards the mirror, the displacement of the image will be [NEET 2018]$ (1) $30 cm towards the mirror$ (2) $36 cm away from the mirror$ (3) $30 cm away from the mirror$ (4) $36 cm towards the mirror$ 392. $Formation of real image using a biconvex lens is shown below: If the whole set up is immersed in water without disturbing the object and the screen positions, what will one observe on the screen ?$ (1) $Image disappears$ (2) $Magnified image$ (3) $Erect real image$ (4) $No change$ 393. $A point object is moving uniformly towards the pole of a concave mirror of focal length 25 cm along its axis as shown below. The speed of the object is 1 m s^{- 1} . At t = 0, the distance of the object from the mirror is 50 cm . The average velocity of the image formed by the mirror between time t = 0 and t = 0.25 s is$ (1) $Zero$ (2) $40 cm s^{- 1}$ (3) $Infinity$ (4) $20 cm s^{- 1}$ 394. $What is the position and nature of image formed by lens combination shown in figure? f_{1}, f_{2} are focal lengths)$ (1) $70 cm from point B at left; virtual$ (2) $40 cm from point B at right; real$ (3) $\frac{20}{3} from point B at right, real$ (4) $70 cm from point B at right; real$ 395. $Two plane mirrors are inclined at 7 0^{o} . A ray incident on one mirror at angle, θ after reflection falls on second mirror and is reflected from there parallel to first mirror. The value of θ is$ (1) $4 5^{o}$ (2) $3 0^{o}$ (3) $5 5^{o}$ (4) $5 0^{o}$ 396. $Find the distance of the image from object O, formed by the combination of lenses in the figure :$ (1) $75cm$ (2) $10cm$ (3) $20cm$ (4) $infinity$ 397. $A short straight object of height 100 cm lies before the central axis of a spherical mirror whose focal lengthhas absolute value \| f \| = 40 cm . The image of object produced by the mirror is of height 25 cm and has thesame orientation of the object. One may conclude from the information:$ (1) $Image is real, same side of concave mirror.$ (2) $Image is virtual, opposite side of convex mirror.$ (3) $Image is virtual, opposite side of concave mirror.$ (4) $Image is real, same side of convex mirror.$ 398. $When one light ray is reflected from a plane mirror with 30° angle of reflection, the angle of deviation of the ray after reflection is:$ (1) $120°$ (2) $110°$ (3) $140°$ (4) $130°$ 399. $The following figure represents two biconvex lenses L_{1} and L_{2} having focal length 10 cm and 15 cm respectively. The distance between L_{1} & L_{2} is :$ (1) $10 cm$ (2) $35 cm$ (3) $25 cm$ (4) $15 cm$ 400. $For a given lens, the magnification was found to be twice as large as when the object was 0.15 m distant from it as when the distance was 0.2 m . The focal length of the lens is$ (1) $0.15 m$ (2) $0.20 m$ (3) $0.10 m$ (4) $0, 05 m$ 401. $The angles of incidence and emergence of a light ray passing through a prism of angle A are i and e respectively. The total deviation produced by the prism is$ (1) $i + e + A$ (2) $i + e - A$ (3) $i + e - 2 A$ (4) $i + e + 2 A$ 402. $A point source of light S is placed at a distance L in front of the centre of plane mirror of width d which is hanging vertically on a wall. A man walks in front of the mirror along a line parallel to the mirror,, at a distance 2L as shown below. The distance over which the man can see the image of the light source in the mirror is :$ (1) $d$ (2) $3d$ (3) $\frac{d}{2}$ (4) $2d$ 403. $A transparent cube of side made of a material of refractive index is immersed in a liquid of refractive index A ray is incident on the face at an angle (shown in the figure). Total internal reflection takes place at point on the face Then must satisfy:$ (1) $θ < sin^{- 1} \frac{μ _{1}}{μ _{2}}$ (2) $θ > sin^{- 1} \frac{μ _{2}^{2}}{μ _{1}^{2}} - 1$ (3) $θ < sin^{- 1} \frac{μ _{2}^{2}}{μ _{1}^{2}} - 1$ (4) $θ > sin^{- 1} \frac{μ _{1}}{μ _{2}}$ 404. $A prism of angle and refractive index 3 is coated with thin film of refractive index 1.5 only at the back exit surface. To have total internal reflection at the back exit surface the incident angle must be ____ and$ (1) $15^{\circ}$ (2) $> 25^{\circ}$ (3) $between 15^{\circ} and 20^{\circ}$ (4) $Both (a) & (c)$ 405. $The lower half of vessel of depth is filled with a liquid of refractive index and the upper half with a liquid of refractive index . The apparent depth of the vessel seen perpendicularly is$ (1) $d (\frac{μ _{1} μ _{2}}{μ _{1} + μ _{2}})$ (2) $d (\frac{1}{μ _{1}} + \frac{1}{μ _{2}})$ (3) $2 d (\frac{1}{μ _{1}} + \frac{1}{μ _{2}})$ (4) $2 d (\frac{1}{μ _{1} μ _{2}})$ 406. $Given is a thin convex lens of glass (refractive index ) and each side having radius ofcurvature . One side is polished for complete reflection. At what distance from the lens, an object be placed on the optic axis so that the image gets formed on the object itself?$ (1) $R / μ$ (2) $R / (2 μ - 3)$ (3) $μR$ (4) $R / (2 μ - 1)$ 407. $Time taken by light to travel in two different materials A and B of refractive indices and of same thickness is and respectively. If s and the ratio of to is 1 : 2. Then the thickness of material, in meter is : (Given and are velocities of light in A and B materials respectively).$ (1) $5x 1 0^{- 10} v_{a} m$ (2) $5 x 1 0^{- 10} m$ (3) $1.5 x 1 0^{- 10} m$ (4) $5 x 1 0^{- 10} v_{b} m$ 408. $A beam of light propagating at an angle α_{1} from a medium 1 through to another medium 2 at an angle α_{2} . If the wavelength of light in medium 1 is λ_{1}, then the wavelength of light in menium 2, (λ_{2}), is$ (1) $\frac{s i n α _{2}}{s i n α _{1}} λ_{1}$ (2) $\frac{sin α _{1}}{sin α _{2}} λ_{2}$ (3) $\frac{α _{1}}{α _{2}} λ_{1}$ (4) $λ_{1}$ 409. $Given below are two statements: Statement (I) : When an object is placed at the centre of curvature of a concave lens, image is formed at the centre of curvature of the lens on the other side. Statement (II) : Concave lens always forms a virtual and erect image. In the light of the above statements, choose the correct answer from the options given below :$ (1) $Both Statement I and Statement II are true$ (2) $Both Statement I and Statement II are false$ (3) $Statement I is true but Statement II is false$ (4) $Statement I is false but Statement II is true$ 410. $At the interface between two materials having refractive indices and , the critical angle for reflection of an em wave is . The material is replaced by another material having refractive index such that the critical angle at the interface between and materials is . If ; and , then is$ (1) $sin^{- 1} (\frac{1}{6})$ (2) $sin^{- 1} (\frac{1}{3})$ (3) $sin^{- 1} (\frac{- 5}{6})$ (4) $sin^{- 1} (\frac{2}{3})$ 411. $In finding out refractive index of glass slab the following observations were made through travelling microscope 50 vernier scale division divisions on main scale in each cmFor mark on paperFor mark on paper seen through slabFor powder particle on the top surface of the glass slab(MSR Main Scale Reading, Vernier Coincidence)Refractive index of the glass slab is:$ (1) $1.52$ (2) $1.35$ (3) $1.42$ (4) $1.24$ 412. $Rainbow is formed due to$ (1) $scattering and refraction$ (2) $internal reflection and dispersion$ (3) $reflection only$ (4) $diffraction and dispersion.$ 413. $Consider following statements for refraction of light through prism, when angle of deviation is minimum.(A) The refracted ray inside prism becomes parallel to the base.(B) Larger angle prisms provide smaller angle of minimum deviation.(C) Angle of incidence and angle of emergence becomes equal.(D) There are always two sets of angle of incidence for which deviation will be same except at minimum deviation setting.(E) Angle of refraction becomes double of prism angle.Choose the correct answer from the options given below:$ (1) $A, B and E Only$ (2) $B, C and D Only$ (3) $B, D and E Only$ (4) $A, C and D Only$ 414. $Interference is possible in$ (1) $light waves only$ (2) $sound waves only$ (3) $both light and sound waves$ (4) $neither light nor sound waves.$ 415. $Blue colour of sea water is due to$ (1) $image of sky in water$ (2) $refraction of sunlight$ (3) $interference of sunlight reflected from the water surface$ (4) $scattering of sunlight by the water molecules$ 416. $Blue colour of the sky is due to$ (1) $reflection of light$ (2) $refraction of light$ (3) $diffraction of light$ (4) $scattering of light$ 417. $Myopia is due to$ (1) $Elongation of eye ball$ (2) $Irregular change in focal length$ (3) $Shortening of eye ball$ (4) $Older age$ 418. $The graph between and for a thin convex lens in order to determine its focal length is plotted as shown in the figure. The refractive index of length is 1.5 and its both the surfaces have same radius of curvatures R. The value of R will be ____cm. (Where u = object distance, v = image distance)$ 419. $A bi convex lens of focal length 10 cm is cut in two identical parts along a plane perpendicular to the principal axis. The power of each lens after cut is_____D$ 420. $The driver sitting inside a parked car is watching vehicles approaching from behind with the help of his side view mirror, which is a convex mirror with radius of curvature R = 2 m . Another car approaches him from behind with a uniform speed of 90 km / hr . When the car is at a distance of 24 m from him, the magnitude of the acceleration of the image of the car in the side view mirror is ' a '. The value of 100 a is m / s^{2} .$