Ncert – class 8- science – Chapter 9 – Light – Reflection and Refraction 2 Welcome to your Ncert - class 8- science - Chapter 9 – Light – Reflection and Refraction 2 1. (Position of the object)(Magnification)(I) An object is placed at focus before a convex mirror(A) Magnification is -∞(II) An object is placed at centre or curvature before a concave mirror(B) Magnification is 0.5(III) An object is placed at focus before a concave mirror(C) Magnification is +1(IV) An object is placed at centre or curvature before a convex mirror(D) Magnification is -1 (E) Magnification is 0.33 I−A,II−D,III−C,IV−B I−C,II−B,III−A,IV−E I−B,II−E,III−D,IV−C I−B,II−D,III−A,IV−E None 2. Why is convex lens used as a magnifying glass It forms magnified image It forms real image It forms virtual image It forms erect image None 3. The radius of curvature of a concave mirror is 40 cm and the size of the real image is twice as that of an object, then the object distance is: 20 cm 30 cm 40 cm 60 cm None 4. A concave mirror of focal length 15 cm forms an image having twice the linear dimensions of the object. The position of the object when the image is virtual will be 7.5 cm 30 cm 22.5 cm 45 cm None 5. Two objects A and B when placed in placed in turn in front of a concave mirror of focal length 7.5 cm give images of equal size. If A is three times the size of B and is placed 30 cm from the mirror, find the distance of B from the mirror. -17.5 cm -15 cm -11 cm 25 cm None 6. In the case of a convex mirror, the image distance is taken to be positive because: None of these Image is formed in front of the mirror centre of curvature and focus lies behind the convex mirror Image is always formed behind the mirror None 7. Which mirror is to be used to obtain a parallel beam of light from a point source? Plane mirror Concave mirror None of these. convex mirror None 8. The absolute refractive indices of water glass and diamond are 1.77, 1.50, and 2.72 respectively, which medium is most optically denser? Glass Diamond None Water None 9. Distances measured perpendicular to and below the principal axis are taken as ________. positive one negative zero None 10. An object is placed at a distance of 16cm from a convex mirror of focal length 20cm, the position of image with its nature is Virtual, erect behind the mirror at 89 cm Virtual, erect behind the mirror at 8.9 cm Real, erect behind the mirror at 8.9 cm Virtual, inverted behind the mirror at 89 cm None 11. The refractive indices of glass and water are 3/ 2 and 4/ 3 respectively. The refractive index of glass with respect to water is 9/8 5/3 2 8/9 None 12. Where can we see an image formed the lens of an object? On the opposite side of the object On the lens itself On the object itself On the same side of the object None 13. Sunlight that bounces off a surface is said to be __________ from the surface. Absorbed Radiated Emitted Reflected None 14. An object of size 7.5 cm is placed in front of a convex mirror of radius of curvature 25 cm at a distance of 40 cm. The size of the image should be 1.7 cm 2.3 cm 1 cm 0.8 cm None 15. A convex lens is placed somewhere in between an object and a screen. The distance between the object and screen is 48 cm. If the numerical value of the magnification produced by the lens is 3, the focal length of the lens is : 4.5 cm 12 cm 9 cm 16 cm None 16. A glass containing a liquid appears to be half filled when viewed from top, if it is actually two-thirds filled. The refractive index of liquid is 5/4 4/3 7 /6 2 None 17. A thin glass (refractive index 1.5) lens has optical power of -5D in air.Its optical power in a liquid medium with refractive index 1.6 will be: -25 D -1D 25 D 1 D None 18. A ray of light is incident on a glass at an angle of 60º What would be the refractive index of glass, if reflected and refracted rays are perpendicular to each other ? 1/2 $$\frac{3}{2}$$ $$\frac{\sqrt{3}}{2}$$ $$\sqrt{3}$$ None 19. The image formed by a convex mirror of focal length 30 cm is a quarter of the size of the object. The distance of the object from the mirror is- 90cm 60cm 30cm 120cm None 20. The plane through the focus perpendicular to the axis of a mirror or lens is Focus Focal length Pole Focal Plane None Time's up Please Share This Share this content Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Leave a Reply Cancel replyCommentEnter your name or username to commentEnter your email address to commentEnter your website URL (optional) Save my name, email, and website in this browser for the next time I comment.
