Light reflaction and refraction

1. LIGHT Reflection & Refraction A Project Made by Ananya Gupta X C Roll No. 02 K.V. OFD Dehradun

2. Light travels in a straight line, when in it’s path, it meets a boundary, a part of it returns back into the same medium (reflection), while another part crosses the boundary (refraction) (Or is absorbed by the boundary if it is opaque.) Normal Incident Ray Reflected Ray Refracted Ray

3. Reflection Reflection from a mirror Mirror Incident Ray Reflected Ray Normal Angle of Incidence ‘ i ’ Angle of Reflection ‘r’ Rules of reflection Incident ray, reflected ray and normal are in the same plane. Angle of reflection = angle of incidence. A ‘NORMAL’ is an imaginary line at right angles to the reflecting surface.

4. When we change the angle of Incidence the angle of Reflection also changes, such that both remain the same. But when the surface is curved, things change, because now all the normals of the curved surface meet at a point, i.e. the centre of the curve, this point is called the centre of Curvature ‘c’.

5. Representation of images formed by spherical Mirrors, using ray diagrams. To represent mirror images we use any two, out of the following three rays : 1. The ray coming parallel to the axis after reflection goes through the focus ‘f’. c f f c 2. Ray coming through the focus after reflection becomes parallel to the axis. 3. Ray coming through the centre of curvature after reflection re-traces it’s path.

6. Now when we have learned the basics, let’s study the various cases. Case 1. When object is at infinity. In this case all the rays are parallel. Case 2. When the object is in between c and infinity. The image is formed between ‘c’ and ‘f’ and is real, small and inverted. c f f c The point image is at focus, real and Inverted. c f f c

7. Case 3. When the object is at ‘c’. c f f c Case 4. When the object is between ‘c’ and ‘f’. The image formed is real, inverted and equal in size. c f f c The image formed is real, inverted And large.

8. c f f c Case 5. When the object is at focus ‘f’. The reflected rays will meet at infinity, so the image formed at infinity, will be infinitely large, real and inverted. Case 6. When the object is between ‘f’ and mirror. c f f c The image formed is virtual, erect and large.

9. c f f c When we talk of convex mirror, the effective focus lies on the other side of the mirror so there is only one possible case . The image formed is virtual, erect and always smaller then the object. These mirrors are used as rear view mirrors in vehicles. (Often written on them “CAUTION: Objects in the mirror are nearer then they appear” because of the small size of the image, it looks that the objects may be far.)

10. REFRACTION OF LIGHT When a wave crosses a boundary between Medium 1 and Medium 2, the wave changes direction because it changes velocity. Frequency remains constant. Velocity changes as a result of wavelength change.

11. Medium 1 (Air) Medium 2 (Glass) Incident Ray Refracted Ray Normal i r Emergent Ray Displacement Basic Terms Angle of Incidence Angle of refraction Sin i Sin r = Constant 2 1 μ = v1 v2

12. Refraction by Spherical Lenses To represent these images we use any two, out of the following three rays : 1. The ray coming parallel to the axis after refraction goes through the focus ‘f’. 2. Ray coming through the focus after refraction becomes parallel to the axis. 3. Ray coming through the optical centre after refraction goes straight. c f f c

13. Now when we have learned the basics, let’s study the various cases. c f f c c f f c Case 1. When the object is at infinity Rays are parallel The point image at focus is inverted and real. Case 2. When the object is between infinity and ‘c’ The image is formed between ‘f’ and ‘c’ real inverted and small.

14. Case 3. When the object is at ‘c’. c f f c c f f c The image is formed at ‘c’ and is real, inverted and equal in size. Case 4. When the object is between ‘c’ and ‘f’. The image is formed between ‘c’ and infinity, and is large, real and inverted.

15. Case 5. When the object is at focus ‘f’. c f f c c f f c The image is formed at infinity, infinitely large, inverted and real. Case 6. When the object is between ‘f’ and lens. The image formed is virtual, erect and large.

16. When we talk of concave lens the image formed is always virtual, small and erect, because the focus used is on the opposite side of the object. c f f c

17. Sign Convention c f f c Direction of Light o ‘o’ Optical centre Object Image Principal Axis All distances are measured from the Optical Centre. Distances in the direction of light are taken as positive. Distances opposite to the direction of light are taken as negative. Distances above the principal axis are + ve while those below the axis are – ve . U - ve V + ve f + ve f - ve Height of Object + ve Height of Image - ve

18. THE END I AM THANKFUL TO WIKIPEDIA WWW.PHYSICS FOR FUN NCERT SCIENCE BOOK FOR X MS POWER POINT MY PARENTS