Refraction Through Lenses Worksheet PDF

Refraction through Lenses – WORKSHEET 1. The first and second focal lengths are equal i.e. f1 = f2 (numerically) when (a) When the lens is placed on the surface of water (b) When the lens is placed on the surface of oil (c) When the lens is placed inside water (d) None of the above SA 2. W...

Refraction through Lenses – WORKSHEET 1. The first and second focal lengths are equal i.e. f1 = f2 (numerically) when (a) When the lens is placed on the surface of water (b) When the lens is placed on the surface of oil (c) When the lens is placed inside water (d) None of the above SA 2. Which of the following lens has virtual focus? (a) Short focal length lens (b) Long focal length lens (c) Bi-convex lens (d) Bi-concave lens AR 3. A double convex lens of glass has a focal length of 10cm in air. When immersed in water, the focal length will be: a) 7.5 cm (b) 10.0 cm (c)- 10 cm (d) 40 cm AD 4. The focal length of a thick convex lens is _______ that of a thin convex lens. a) More than (b) less than (c) equal to (d) double of 5. An object is placed at the focus of a concave lens. Where will be the image? (a) At infinity (b) Away from 2F (c) Between 2F and F (d) Between F and O 6. The magnification of ____________ lens is always less than 1. (a) Short focal length lens (b) Long focal length lens c) Bi-convex lens (d) Bi-concave lens 7. A beam of parallel light rays incident obliquely converges at ____________ after refraction through a convex lens. (a) At the second focal length (b) at some point on the second focal plane (c) at some point on the principal axis (d) At some point on the first focal plane SA 8. If a lens deviates the ray towards its centre, the power is __________. (a) Positive (b) Negative (c) infinity (d) zero 9. A person suffering from long sightedness or Hypermetropia wears spectacles having AR _________. (a) Convex lens (b) concave lens (c) plane mirror (d)glass plate 10. Which of the following statements is true? (a) A convex lens has 4 diopter power having a focal length 0.25 m (b) A convex lens has -4 diopter power having a focal length 0.25 m AD (c) A concave lens has 4 diopter power having a focal length -0.25 m (d) A concave lens has – 4 diopter having a focal 0.25 m Q11. In order to obtain a magnification of (– 3) with a convex lens, object should be placed : a) Between optical centre and focus b) Between focus and 2F c) At 2F d) Beyond 2F Q12. What would be the relative size of the image formed by a convex lens when the object is placed between F and 2F? a) Highly diminished (point sized).b) Enlarged c) At Infinity d) Infinitely large (highly enlarged) Q13. When the refractive index of a medium relative to lens is 1, an oblique incident ray on a convex lens will pass undeviated through it. SA a) Yes b) No Q14. A student obtains a blurred image of a distant object on a screen using a convex lens. To obtain a distinct image on the screen he should move the lens : a) Away from the screen AR b) Towards the screen c) To a position very far away from the screen d) Either towards or away from the screen depending upon the position of the object Q15. The focal lengths of four convex lenses P, Q, R and S are 20 cm, 15 cm, 5 cm and 10cm respectively. The lens having greatest power is : AD a) P b) Q c) R d) S Q16.A double convex lens of glass has a focal length of 10cm in air. When immersed in water, the focal length will be: (a) 7.5 cm (b) 10.0 cm (c) 9.8 cm (d) 40 cm Q17. A concave lens forms (a) Only real images (b) only virtual images (c) both real and virtual images (d) only magnified images Q18.When the object moves from a large distance towards a concave lens, the image shifts from focus towards the ____________. a) Optical centre b) 2F1 c) 2F2 SA d) Infinity Q19. A person suffering from long sightedness or Hypermetropia wears spectacles having _________. (a) Convex lens (b) concave lens (c) plane mirror (d)glass plate AR Q20. Name the point which is on the principal axis of the lens such that that a ray of light passing through this point emerges parallel to its direction of incidence. (a) First Focal point (b) Centre of Curvature AD (c) Second Focal point (d) Optical Centre 21. Name the lens and position of the object for the following - a) Image is enlarged and inverted b) Image is diminished and inverted c) Image is enlarged and erect d) Image is diminished and erect e) Used as burning glass f) Used in Galilean telescope g) Used terrestrial telescope 22. Identify the converging lens- The names of lenses are A,B,C and so on from LHS towards RHS. 23. A convex lens is placed in a fluid whose refractive index is more than the refractive index of the lens. A parallel beam of light in the fluid falls on this lens. What will happen to it? SA 24. Using the sign convention, identify the sign of the following – a) u for concave lens b) f for concave lens c) u for convex lens AR d) f for convex lens AD e) v for real image f) v for virtual image g) Object length for concave lens h) Image length for virtual image 25.What will happen to a ray of light if – a. its incident towards the optical centre of a thick convex lens b. its incident towards the optical centre of a thin concave lens 26. Draw the following ray diagrams- a. Simple microscope use b. Lens for myopic eye SA AR AD