2. By J.Saranya PGT Physics

3. OPTICS Rectilinear propagation Laws of reflection and refraction Ray optics Interference, diffraction polarisation Wave optics

4. OPTICAL PHENOMENON a) Reflection

5. b) Refraction

6. c)Absorption

7. A) Reflection bouncing back of light

8. LAWS OF REFLECTION Angle of incidence is equal to the angle of reflection i = r The incident ray, the reflected ray and the normal all lie in the same plane. IMAGE It is a point where atleast two light rays actually meet or appear to meet.  Real image  Virtual image

9. Real image Virtual image light rays actually meet after reflection. Can be obtained on screen. Inverted. Eg., image formed on cinema screen. light rays diverge after reflection. Can’t be obtained on screen. Erect Eg., image formed by plane mirror or convex mirror

11. Spherical Mirrors A spherical mirror has the shape of a section of a sphere. If the outside is mirrored, it is convex; if the inside is mirrored, it is concave.

12. SPHERICAL MIRRORS

16. RELATION BETWEEN FOCAL LENGTH AND RADIUS OF CURVATURE R = 2f f = R / 2

17. CONCAVE MIRROR f = R / 2

18. CONVEX MIRROR f = R / 2

20. MIRROR FORMULA FOR CONCAVE MIRROR OO’C and II’C are similar triangles OO’ = CO II’ IC II’F and NAF are similar triangles NA = NF II’ FI OO’ = NF II’ FI (But NA = OO’) CO = PF (NF = PF) IC FI PO-PC = PF PC-PI PI-PF -u + R = -f ( since R = 2f ) -u + 2f = -f -R + v -v + f -2f = v -v + f 1 + 1 = 1 v u f Valid cases : 1. Object based on principal axis 2. Small aperture 3. In paraxial rays

21. MIRROR FORMULA FOR CONVEX MIRROR OO’C and II’C are similar triangles OO’ = CO II’ IC II’F and NAF are similar triangles NA = NF II’ IF OO’ = NF II’ IF But NA = OO’ OC = PF NF = PF IC IF PO+PC = PF PC-PI PF-PI -u + R = f since R = 2f -u + 2f = f R - v f - v 2f - v f - v 1 + 1 = 1 v u f

22. Mirror Equation Sample Problem Suppose AllStar, who is 3 and a half feet tall, stands 27 feet in front of a concave mirror with a radius of curvature of 20 feet. Where will his image be reflected and what will its size be? d i = h i = CF -15.88 feet -2.06 feet

23. MIRROR EQUATION SAMPLE PROBLEM 2 CF Casey decides to join in the fun and she finds a convex mirror to stand in front of. She sees her image reflected 7 feet behind the mirror which has a focal length of 11 feet. Her image is 1 foot tall. Where is she standing and how tall is she? d o = h o = 19.25 feet - 2.75 feet

24. LINEAR MAGNIFICATION BY SPHERICAL MIRRORS The linear magnification produced by a spherical mirror is the ratio of the size of the image formed by the mirror to the size of the Object, both measured perpendicular to the principal axis. m = h i h o OO’P and II’P are similar triangles II’ = PI OO’ PO Since II’ = -h i ; OO’ = h o ; PI = - v ; PO = - u - h i = - v or h i = - v h o u h o u m = - v u

25. 1 + 1 = 1 v u f OTHER FORMULA FOR MAGNIFICATION m = f – v m = f f f - u Real, invertedVirtual, erect