Ray Optics PYQs Set 14 (PDF)

Set 14 of 16 · Questions 391-420 of 467

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Mere Teacher · Previous Year Questions NEET Physics · Ray Optics · Set 14 (Q391-420)
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391. $When objects at different distances are seen by the eye, which of the following remains constant$ (1) $The focal length of the eye lens$ (2) $The object distance from the eye lens$ (3) $The radii of curvature of the eye lens$ (4) $The image distance from the eye lens$ 392. $A thin convex lens of focal length 5 cm and a thin concave lens of focal length 4 cm are combined together (without any gap) and this combination has magnification m_{1} when an object is placed 10 cm before the convex lens. Keeping the positions of convex lens and object undisturbed a gap of 1 cm is introduced between the lenses by moving the concave lens away, which lead to a change in magnification of total lens system to m_{2} . The value of (\frac{m _{1}}{m _{2}}) is____.$ (1) $\frac{5}{9}$ (2) $\frac{5}{27}$ (3) $\frac{3}{2}$ (4) $None of the above$ 393. $An object is moving away from concave mirror of focal length f starting from focus. The distance of an object from pole of mirror is x . The correct graph of magnitude of magnification (m) verses distance x is:$ (1) (2) (3) (4) 394. $Image formed on retina of eye is proportional to$ (1) $Size of object$ (2) $Area of object$ (3) $\frac{S i z eo f o bj ec t}{S i z eo f ima g e}$ (4) $\frac{s i z eo f ima g e}{s i z eo f o bj ec t}$ 395. $If there had been one eye of the man, then$ (1) $Image of the object would have been inverted$ (2) $Visible region would have decreased$ (3) $Image would have not been seen three dimensional$ (4) $(b) and (c) both$ 396. $A tall man of height 6 feet, want to see his full image. Then required minimum length of the mirror will be$ (1) $12 feet$ (2) $3 feet$ (3) $6 feet$ (4) $any length.$ 397. $Pick the wrong answer in the context with rainbow.$ (1) $Rainbow is a combined effect of dispersion, refraction and reflection of sunlight.$ (2) $When the light rays undergo two internal reflections in a water drop, a secondary rainbow is formed.$ (3) $The order of colours is reversed in the secondary rainbow.$ (4) $An observer can see a rainbow when his front is towards the sun.$ 398. $A parallel beam of light is incident on a converging lens parallel to its principal axis. As one moves away from the lens on the other side of the principal axis, the intensity of light$ (1) $first decreases and then increases$ (2) $continuously increases$ (3) $continuously decreases$ (4) $first increases and then decreases.$ 399. $A man is suffering from colour blindness for green colour. To remove this defect, he should use goggles of$ (1) $Green colour glasses$ (2) $Red colour glasses$ (3) $Smoky colour glasses$ (4) $None of the above$ 400. $A camera objective has an aperture diameter d. If the aperture is reduced to diameter d /2, the exposure time under identical conditions of light should be made$ (1) $2 fold$ (2) $2 fold$ (3) $22 fold$ (4) $4 fold$ 401. $The focal length f is related to the radius of curvature r of the spherical convex mirror by -$ (1) $f = r$ (2) $f = - \frac{1}{2} r$ (3) $f = + \frac{1}{2} r$ (4) $f = - r$ 402. $Formation of real image using a biconvex lens is shown below :$ (1) $Erect real image$ (2) $No change$ (3) $Image disappears$ (4) $Magnified image$ 403. $A lens is placed between a source oflight and a wall. It forms images of area A_{1} and A_{2} on the wall, for its two different positions. The area of the source oflight is$ (1) $\frac{A _{1} - A _{2}}{2}$ (2) $\frac{1}{A _{1}} + \frac{1}{A _{2}}$ (3) $A_{1} A_{2}$ (4) $\frac{A _{1} + A _{2}}{2} .$ 404. $Two plane mirrors are inclined to each other such that a ray of light incident on the first mirror (M_{1}) and parallel to the second mirror (M_{2}) is finally reflected from the second mirror (M_{2}) parallel to the first mirror (M_{1}). The angle between the two mirrors will be :$ (1) $75º$ (2) $90º$ (3) $45º$ (4) $60º$ 405. $A plano convex lens is made of refractive index 1.6. The radius of curvature of the curved surface is 60 cm. The focal length of the lens is$ (1) $200 cm$ (2) $100 cm$ (3) $50 cm$ (4) $400 cm.$ 406. $A double convex lens has focal length 25 cm. The radius of curvature of one of the surfaces is double of the other. Find the radii if the refractive index of the material of the lens is 1.5.$ (1) $100 cm, 50 cm$ (2) $25 cm, 50 cm$ (3) $18.75 cm, 37.5 cm$ (4) $50 cm, 100 cm$ 407. $In a Fresnel biprism experiment, the two positions of lens give separation between the slits as 16 cm and 9 cm respectively. What is the actual distance of separation?.$ (1) $13 cm$ (2) $14 cm$ (3) $12.5 cm$ (4) $12 cm.$ 408. $Time taken by sunlight to pass through a window of thickness 4 mm whose refractive index is is$ (1) $2 \times 1 0^{- 4} s$ (2) $2 \times 1 0^{8} s$ (3) $2 \times 1 0^{- 11} s$ (4) $2 \times 1 0^{11} s .$ 409. $A beam of light from a souce L is incident normally on a plane mirror fixed at a certain distance x from the source. The beam is reflected back as a spot on a scale placed just above the source L. When the mirror is rotated through a small angle θ, the spot of the light is found to move through a distance y on the scale. The angle θ is given by :$ (1) $\frac{y}{2 x}$ (2) $\frac{y}{x}$ (3) $\frac{x}{2 y}$ (4) $\frac{x}{y}$ 410. $The refracting angle of a prism is A and refractive index of the material of the prism is cot (A/2). Then the angle of minimum deviation will be –$ (1) $180-2A$ (2) $90-A$ (3) $180+ 2A$ (4) $180-3A$ 411. $Two identical glass (μ_{g} = 3/2) equiconvex lenses of focal length f each are kept in contact. The space between that two lenses in filled with water (μ_{w} = 4/3). The focal length of the combination is$ (1) $\frac{3 f}{4}$ (2) $\frac{f}{3}$ (3) $f$ (4) $\frac{4 f}{3}$ 412. $In Young’s experiment, two coherent sources are placed 0.90 mm apart and fringes are observed one metre away. If it produces second dark fringe at a distance of 1 mm from central fringe, the wavelength of monochromatic light is used would be$ (1) $60 \times 1 0^{- 4} c m$ (2) $10 \times 1 0^{- 4} c m$ (3) $10 \times 1 0^{- 5} c m$ (4) $6 \times 1 0^{- 5} c m .$ 413. $A prism of refractive index and angle of prism A is placed in the position of minimum angle of deviation. If minimum angle of deviation is also A, then in terms of refractive index$ (1) $2 cos^{- 1} (\frac{μ}{2})$ (2) $sin^{- 1} (\frac{μ}{2})$ (3) $sin^{- 1} (\frac{μ - 1}{2})$ (4) $cos^{- 1} (\frac{μ}{2})$ 414. $The exposure time of a camera a lens at f/2.8 setting is 1/200 seconds. The correct time of exposure for f/5.6 setting is -$ (1) $0.04 sec$ (2) $0.20 sec$ (3) $0.40 sec$ (4) $0.02 sec$ 415. $Two identical symmetric double convex lenses of focal length f are cut into two equal parts L_{1}, L_{2} by AB plane and L_{3}, L_{4} by XY plane as shown in figure respectively. The ratio of focal lengths of lenses L_{1} and L_{3} is$ (1) $1 : 1$ (2) $1 : 2$ (3) $1 : 4$ (4) $2 : 1$ 416. $The frequency of a light wave in a material is and wavelength is . The refractive index of material will be$ (1) $1.50$ (2) $3.00$ (3) $1.33$ (4) $1.40.$ 417. $When a biconvex lens of glass having refractive index 1.47 is dipped in a liquid, it acts as a plane sheet of glass . This implies that the liquid must have refractive index.$ (1) $equal to that of glass$ (2) $less then one$ (3) $greater than that of glass$ (4) $less then that of glass$ 418. $The angle incidence for a ray of light at a refracting surface of a prism is 45º. The angle of prism is 60º. If the ray suffers minimum deviation through the prism, the angle of minimum deviation and refractive index of the material of the prism respectively, are$ (1) $30º; \frac{1}{2}$ (2) $45º ; \frac{1}{2}$ (3) $30º ; 2$ (4) $45º ; 2$ 419. $A plano convex lens of refractive index and focal length is kept in contact with another plano concave lens of refractive index and focal length . If the radius of curvature of their spherical faces is R each and = , then and are related as :$ (1) $2μ1 - μ2 = 1$ (2) $μ1 + μ2 = 3$ (3) $3μ2 - 2μ1 = 1$ (4) $2μ2 - μ1 = 1$ 420. $Let u and v be the distances of the object and the image from a lens of focal length f . The correct graphical representation of u and v for a convex lens when \| u \| >, is$ (1) (2) (3) (4)