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Physics

Physics. Lenses. CONTENT. Lenses-Introduction and types Important Terminologies related to lenses Images formed by convex lenses Images formed by concave lenses Uses of concave and convex lenses. REFRACTION OF LIGHT.

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Physics

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  1. Physics Lenses

  2. CONTENT • Lenses-Introduction and types • Important Terminologies related to lenses • Images formed by convex lenses • Images formed by concave lenses • Uses of concave and convex lenses

  3. REFRACTION OF LIGHT • The change in the direction of light when it passes from one medium to another is called refraction of light.

  4. REFRACTION OF LIGHT Incident Ray Normal Rarer medium i Interface Denser medium r Refracted Ray • When a ray of light goes from rarer to denser medium, the refracted ray bends towards the normal in the denser medium.

  5. REFRACTION OF LIGHT Normal Refracted Ray Rarer medium r Interface Denser medium i Incident Ray • If the ray of light travels from denser to rarer medium, the refracted ray bends away from the normal.

  6. It is a transparent material bounded by two surfaces, of which one or both surfaces are curved. There are two types of spherical lenses, namely, Convex lens Concave lens LENSES

  7. CONVEX/ CONVERGING LENSES It is thick at the middle and thinner at the edges.

  8. Convex /Converging - Types

  9. Convex/ Diverging Lenses It is thin at the middle and thicker at the edges.

  10. Convex/ Diverging Lenses- Types

  11. Convex Lens-Centre of curvature C1 C2 centre of curvature ‘C’

  12. Concave Lens-Centre of curvature

  13. Convex Lens- Radius of curvature C2 C1 O It is the radius of sphere of which the lens is a part. OC1 and OC2 are the two radii of curvature.

  14. Concave Lens- Radiusof curvature O OC1 and OC2 are the two radii of curvature.

  15. Concave and Convex Lens- Principal Axis Principal axis is the line passing through he optical centre of the lens and perpendicular to both the faces of the lens. In the diagram, AB is the principal axis. O B A B A

  16. Concave and Convex Lens- Optical centre It is the geometrical centre of the lens. Any ray passing through the optical centre of lens remains undeviated. In the diagram, point O is the optical centre. O B A B A

  17. Convex Lens- Principal focus C2 C1 F2 F1 Rays of light incident parallel to the principal axis meet after refraction, at the point on the other side of the lens on the principal axis. This is called the principal focus. A convex lens has two principal foci F1 and F2 as rays can be refracted from either side.

  18. ConcaveLens- Principal focus F2 F1 Rays of light incident parallel to the principal axis appear to diverge, after refraction, from a point on the same side of the lens on the principal axis. This is called the principal focus. A concave lens has two principal foci F1 and F2.

  19. Convex Lens- Focal Length (f) F2 F1 O f focal length The distance between the principal focus and the optical center is called the focal length (f).

  20. Concave Lens- Focal Length (f) F2 F1 O The distance between the principal focus and the optical center is called the focal length (f).

  21. What do you suppose will happen to the focal length of lens if the curvature of the lens is increased? (a) Increases (b) Decreases (c) Remains same (b) Decreases

  22. Representation of Lens as a Combination of Different Sections of Prism

  23. Image formed by Lenses Rule 1 Incident ray Refracted ray O F1 F2 All the rays parallel to the principal axis of a convex lens converge at the focus on the other side of the lens after refraction.

  24. Rule 1 Image formed by Lenses O F All the rays parallel to the principal axis of a concave lens appear to diverge from the focal point after refraction through the lens.

  25. Rule 2 Image formed by Lenses O F1 F2 Incident ray Refracted ray The ray passing through the optical centre of a lens remains undeviated irrespective of its inclination on the principal axis.

  26. Rule 2 Image formed by Lenses O F1 F2 The ray passing through the optical centre of a lens remains undeviated irrespective of its inclination on the principal axis.

  27. Rule 3 Image formed by Lenses O F1 F2 Incident ray Refracted ray • The ray passing through the focus of the lens becomes parallel to the principal axis after passing through the lens.

  28. Rule 3 Image formed by Lenses O F All the rays appear to come towards focus, become parallel to principal axis after passing through the lens.

  29. Convex lens/ Converging lenses: F Converging refracted rays Incident rays

  30. IMAGE FORMATION BY CONVEX LENS

  31. OBJECT AT INFINITY M M Object placed at infinity Object placed at infinity F2 B F1 F1 F2 O O A N N

  32. OBJECT BEYOND 2F M A F2 C2 C1 B’ B O 2F1 2F2 F1 A’ N

  33. OBJECT AT 2F M A 2F1 C1 F2 B’ C2 B O F1 2F2 A’ N

  34. OBJECT BETWEEN 2F AND F M A F2 C2 C1 B’ B O 2F1 2F2 F1 A’ N

  35. OBJECT AT F A O F2 B F1

  36. OBJECT BETWEEN F AND O A’ AB — Object A’B’ — Image A A1 B O F2 F1 B’

  37. IMAGE FORMATION BY CONVEX LENS

  38. Concave lens/ Diverging lenses: F Diverging refracted rays Incident rays

  39. IMAGE FORMATION BY CONCAVE LENS

  40. Object At Infinity M Object at infinity O F N

  41. Object Any where M A A’ O B F B’ N

  42. IMAGE FORMATION BY CONCAVE LENS

  43. Uses of Convex Lens camera picture projector telescope microscope

  44. Uses of Convex Lens Used in spectacles for the correction of long sightedness of the eyes Used as a reading lens

  45. Uses of Concave Lens Used in spectacles for the correction of short sightedness of the eyes Used in telescopes to see far off objects

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