Tiêu đề 9.RAY OPTICS AND OPTICAL INSTRUMENTS - Questions.pdf ✅

9.RAY OPTICS AND OPTICAL INSTRUMENTS (1.)The distance between a point source of light and a screen which is 60 cm is increased to 180 cm. The intensity on the screen as compared with the original intensity will be (a.) (1/9) times (b.) (1/3) times (c.) 3 times (d.) 9 times (2.)A thin lens made of glass of refractive index μ = 1.5 has a focal length equals is 12 cm in air. It is now immersed in water (μ = 4 3 ). Its new focal length is (a.) 48 cm (b.) 36 cm (c.) 24 cm (d.) 12 cm (3.)The focal length of an objective of a telescope is 3 metre and diameter 15 cm. Assuming for a normal eye, the diameter of the pupil is 3 mm for its complete use, the focal length of eye piece must be (a.) 6 cm (b.) 6.3 cm (c.) 20 cm (d.) 60 cm (4.)The minimum magnifying power of a telescope is M, If the focal length of its eye lens is halved, the magnifying power will become (a.) M/2 (b.) 2 M (c.) 3 M (d.) 4 M (5.)A plane mirror makes an angle of 30° with horizontal. If a vertical ray strikes the mirror, find the angle between mirror and reflected ray (a.) 30° (b.) 45° (c.) 60° (d.) 90° (6.)The focal lengths of the objective and the eye- piece of a compound microscope are 2.0 cm and 3.0 cm respectively. The distance between the objective and the eye-piece is 15.0 cm. The final image formed by the eye-piece is at infinity. The two lenses are thin. The distances in cm of the object and the image produced by the objective measured from the objective lens are respectively (a.) 2.4 and 12.0 (b.) 2.4 and 15.0 (c.) 2.3 and 12.0 (d.) 2.3 and 3.0 (7.)Image formed on retina of eye is proportional to (a.) Size of object (b.) Area of object (c.) Size of object Size of image (d.) Size of image Size of object (8.)The power of the combination of a convex lens of focal length 50 cm and concave lens of focal length 40 cm is (a.) +1 D (b.) -1 D (c.) Zero (d.) -0.5 D (9.)Resolving power of a microscope depends upon (a.) The focal length and aperture of the eye lens (b.) The focal lengths of the objective and the eye lens (c.) The apertures of the objective and the eye lens (d.) The wavelength of light illuminating the object (10.)If a lens is cut into two pieces perpendicular to the principal axis and only one part is used, the intensity of the image (a.) Remains same (b.) 1 2 times (c.) 2 times (d.) Infinite (11.)A hollow double concave lens is made of very thin transparent material. It can be filled with air or either of two liquids L1 and L2 having refractive indices n1 and n2 respectively (n2 > n1 > 1). The lens will diverge a parallel beam of light if it is filled with (a.) Air and placed in air (b.) Air and immersed in L1 (c.) L1 and immersed in L2 (d.) L2 and immersed in L1 (12.)Given figures show the arrangements of two lenses, The radii of curvature of all the curved surfaces are same. The ratio of the equivalent focal length of combinations P,Q and R is (a.) 1 ∶ 1 ∶ 1 (b. ) 1 ∶ 1 ∶ −1
(c.) 2 ∶ 1 ∶ 1 (d. ) 2 ∶ 1 ∶ 2 (13.)The intensity of direct sunlight on a surface normal to the rays is I0. What is the intensity of direct sunlight on a surface, whose normal makes an angle of 60° with the rays of the sun (a.) I0 (b.) I0 ( √3 2 ) (c.) I0 2 (d.) 2I0 (14.)A source of light emits a continuous stream of light energy which falls on a given area. Luminous intensity is defined as (a.) Luminous energy emitted by the source per second (b.) Luminous flux emitted by source per unit solid angle (c.) Luminous flux falling per unit area of a given surface (d.) Luminous flux coming per unit area of an illuminated surface (15.)The dispersive powers of crown and flint glasses are 0.02 and 0.04 respectively. In an achromatic combination of lenses the focal length of flint glass lens is 40 cm. The focal length of crown glass lens will be (a.) −20 cm (b.) +20 cm (c.) −10 cm (d.) +10 cm (16.)The reason of seeing the Sun a little before the sunrise is (a.) Reflection of the light (b.) Refraction of the light (c.) Scattering of the light (d.) Dispersion of the light (17.)A thin plano-convex lens of focal f is split into two halves. One of the halves is shifted along the optical axis. The separation between object and image plane is 1.8 m. The magnification of the image formed by one of the half lens is 2. Find the focal-length of the lens and separation between the two halves (a.) 0.1 m (b.) 0.4 m (c.) 0.9 m (d.) 1 m (18.)Which mirror is to be used to obtain a parallel beam of light from a small lamp? (a.) Plane mirror (b.) Convex mirror (c.) Concave mirror (d.) Any one of these (19.)Two thin lenses whose powers are +2D and −4D respectively combine, then the power of combination is (a.) −2D (b.) +2D (c.) −4D (d.) +4D (20.)Near and far points of human eye are (a.) 25 cm and infinite (b.) 50 cm and 100 cm (c.) 25 cm and 50 cm (d.) 0 cm and 25 cm (21.)A man’s near point is 0.5 m and far point is 3 m. Power spectacle lenses repaired for (i) reading purposes (ii) seeing distant objects, respectively (a.) −2 D and + 3 D (b.) +2 D and −3 D (c.) +2 D and – 0.33 D (d.) −2 D and + 0.33D (22.)Refractive index of the material of a prism is 1.5. If δm = A, what will be a value of angle of the given prism? (whereδm = minimum deviation;A = angle of prism) (a.) 82.8° (b. ) 41.4° (c.) 48.6° (d. ) 90° (23.)60° prism hasμ = √2. Angle of incidence for minimum deviation is (a.) 45° (b. ) 30° (c.) 60° (d. ) 90° (24.)A layered lens as shown in figure is made of two types of transparent materials indicated by different shades. A point object is placed on its axis. The object will form (a.) 1 image (b.) 2 images (c.) 3 images (d.) 9 images
(25.)A hypermetropic person having near point at a distance of 0.75 m puts on spectacles of power 2.5 D. The near point now is at (a.) 0.75 m (b.) 0.83 m (c.) 0.26 cm (d.) 0.26 m (26.)Lux is equal to (a.) 1 lumen/m2 (b.) 1 lumen/cm2 (c.) 1 candela/m2 (d.) 1 candela/cm2 (27.)The radius of curvature of the convex face of a planoconvex lens is 15 cm and the refractive index of the material is 1.4. Then the power of the lens in diopter is (a.) 1.6 (b.) 1.66 (c.) 2.6 (d.) 2.66 (28.)The Cauchy’s dispersion formula is (a.) n = A + Bλ −2 + Cλ −4 (b.) n = A + Bλ 2 + Cλ −4 (c.) n = A + Bλ −2 + Cλ 4 (d.) n = A + Bλ 2 + Cλ 4 (29.)A 2.0 cm tall object is placed 15 cm in front of a concave mirror of focal length 10 cm. What is the size and nature of the image (a.) 4 cm, real (b.) 4 cm, virtual (c.) 1.0 cm, real (d.) None of these (30.)The plane surface of a plano-convex lens of focal length f is silvered. It will behave as (a.) Plane mirror (b.) Convex mirror of focal length 2 f (c.) Concave mirror of focal length f 2 (d.) None of the above (31.)A medium shows relation between i and r as shown. If speed of light in the medium is nc then value of n is (a.) 1.5 (b.) 2 (c.) 2 −1 (d.) 3 −1/2 (32.)The frequency of a light ray is 6 × 1014Hz. Its frequency when it propagates in a medium of refractive index 1.5, will be (a.) 1.67 × 1014Hz (b.) 9.10 × 1014Hz (c.) 6 × 1014Hz (d.) 4 × 1014Hz (33.)Refractive index of glass with respect to medium is4 3 . If the differences between velocities of light in medium and glass is 6.25 × 107ms−1 , then velocity of light in medium is (a.) 2.5 × 108ms−1 (b. ) 0.125 × 108ms−1 (c.) 1.5 × 108ms−1 (d. ) 3 × 108ms−1 (34.)The ratio of the refractive index of red light to blue light in air is (a.) Less than unity (b.) Equal to unity (c.) Greater than unity (d.) Less as well as greater than unity depending upon the experimental arrangement (35.)A thin convex lens of focal length 10 cm is placed in contact with a concave lens of same material and of same focal length. The focal length of combination will be (a.) Zero (b.) Infinity (c.) 10 cm (d.) 20 cm (36.)A hypermetropic person has to use a lens of power +5 D to normalize his vision. The near point of the hypermetropic eye is (a.) 1 m (b.) 1.5 m (c.) 0.5 m (d.) 0.66 m (37.)The spectrum obtained from a sodium vapour lamp is an example of (a.) Absorption spectrum (b.) Emission spectrum (c.) Continuous spectrum (d.) Band spectrum (38.)If a parallel beam of white light is incident on a converging lens, the colour which is brought to focus nearest to the lens is (a.) Violet (b.) Red (c.) The mean colour (d.) All the colours together (39.)Dispersive power depends on the following (a.) Material of the prism (b.) Shape of the prism (c.) Size of the prism (d.) Size, shape and material of the prism sin r sin i 30°
(40.)The light gathering power of a camera lens depends on (a.) Its diameter only (b.) Ratio of diameter and focal length (c.) Product of focal length and diameter (d.) Wavelength of light used (41.)How will the image formed by a convex lens be affected, if the central portion of the lens is wrapped in blank paper, as shown in the figure (a.) No image will be formed (b.) Full image will be formed but is less bright (c.) Full image will be formed but without the central portion (d.) Two images will be formed, one due to each exposed half (42.)The twinkling effect of star light is due to (a.) Total internal reflection (b.) High dense matter of star (c.) Constant burning of hydrogen in the star (d.) The fluctuating apparent position of the star being slightly different from of the star being different from the actual position of the star (43.)The graph shows how the magnification m produced by a convex thin lens varies with image distance v. What was the focal length of the used lines (a.) b/c (b.) b/ca (c.) bc/a (d.) c/b (44.)A fish, looking up through the water sees the outside world contained in a circular horizon. If the refractive index of water is 4/3 and the fish is 12 cm below the surface of water, the radius of the circle in centimetre is (a.) 12×3 √5 (b.) 12 × 3 × √5 (c.) 12×3 √7 (d.) 12 × 3 × √7 (45.)The wavelength of sodium light in air is 5890Å. The velocity of light in air is 3 × 10−8 ms ̄1. The wavelength of light in a glass of refractive index 1.6 would be close to (a.) 5890Å (b. ) 3681Å (c.) 9424Å (d. ) 15078Å (46.)Focal length of a convex lens of refractive index 1.5 in 2 cm. Focal length of lens when immersed in a liquid of refractive index of 1.25 will be (a.) 10 cm (b.) 2.5 cm (c.) 5 cm (d.) 7.5 cm (47.)A combination of two thin lenses of the same material with focal length f1 and f2, arranged on a common axis minimizes chromatic aberration. If the distance between them is (a.) (f1+f2 ) 4 (b.) (f1+f2 ) 2 (c.) (f1 + f2 ) (d.) 2(f1 + f2 ) (48.)Speed of light is maximum in (a.) Water (b.) Air (c.) Glass (d.) Diamond (49.)A ray of light is incident on a plane mirror at an angle of 60°.The angle of deviation produced by the mirror is (a.) 120° (b. ) 30° (c.) 60° (d. ) 90° (50.)The refractive index of a material of a planoconcave lens is 5/3, the radius of curvature is 0.3 m. The focal length of the lens in air is (a.) -0.45 m (b.) -0.6 m (c.) -0.75 m (d.) -1.0 m (51.)A biconvex lens of focal length 15 cm is in front of a plane mirror. The distance between the lens and the mirror is 10 cm. A small object is kept at a distance of 30 cm from the lens. The final image is (a.) Virtual and at a distance of 16 cm from the mirror (b.) Real and at a distance of 16 cm from the mirror (c.) Virtual and at a distance of 20 cm from the mirror (d.) None of the above (52.)A wave has velocity u in medium P and velocity 2u in medium Q.If the wave is incident in medium P at an angle 30°,then the angle of refraction will be (a.) 30° (b. ) 45° b a c m v