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# Ligth reflection and refraction

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### Ligth reflection and refraction

1. 1. Name - Alwin M Reji Class – X Roll - 8
2. 2. Reflection :: It is the process of sending back Reflection It is the process of sending back the incidents light. the incidents light.   Law of reflection of light: Law of reflection of light: i. The angle of incident is equal to the i. The angle of incident is equal to the angle of reflection. angle of reflection. ii. The incidence ray, the normal to the ii. The incidence ray, the normal to the mirror at the point of incidence and the mirror at the point of incidence and the reflected ray, all lie in the same plane. reflected ray, all lie in the same plane.
3. 3. Reflection from a mirror: Normal Reflected ray Incident ray Angle of incidence Mirror Angle of reflection
4. 4. Texture affects reflection Texture affects reflection Diffuse reflection (rough) Diffuse reflection (rough) reflects light in many different directions, reflects light in many different directions, Specular reflection (smooth) Specular reflection (smooth) reflects light in only one direction reflects light in only one direction Smooth – variations in surface < λ Smooth – variations in surface < λ
5. 5. Light striking a mirror reflects at the same Light striking a mirror reflects at the same angle that it struck the mirror angle that it struck the mirror
6. 6.  These law of reflection are applicable to all type of  These law of reflection are applicable to all type of reflecting surfaces including spherical surface. reflecting surfaces including spherical surface.  Image formed by a plane mirror is always virtual and  Image formed by a plane mirror is always virtual and erect. The size of the image is equal to that of the erect. The size of the image is equal to that of the object. The image formed is as far behind the mirror as object. The image formed is as far behind the mirror as the object is in front of it. It is laterally inverted, i.e., the object is in front of it. It is laterally inverted, i.e., the image is inverted sideways the image is inverted sideways
7. 7. A spherical mirror, whose reflection surface is A spherical mirror, whose reflection surface is curved inwards is called a concave mirror and the curved inwards is called a concave mirror and the one whose reflecting surface is curved outwards is one whose reflecting surface is curved outwards is called a convex mirror. called a convex mirror.
8. 8. Sign of M Orientation of Image Type of Image + Upright Virtual – Inverted Real
9. 9. •• A ray traveling through C will reflect back A ray traveling through C will reflect back through C through C •• A ray traveling through (f) will reflect parallel to A ray traveling through (f) will reflect parallel to the PA the PA •• A ray traveling to the intersection of the PA and A ray traveling to the intersection of the PA and the mirror will reflect at the same angle below the the mirror will reflect at the same angle below the PA. PA. •• A ray traveling parallel to PA will reflect through A ray traveling parallel to PA will reflect through the focal point the focal point
10. 10. Hard Surface
11. 11. Reflective surface is on the outside of Reflective surface is on the outside of the curve. the curve. The points ff and C are located behind The points and C are located behind the mirror the mirror negative negative
12. 12. A ray parallel to the PA will reflect directly away A ray parallel to the PA will reflect directly away from f. from f. A ray towards ff will reflect parallel to the PA A ray towards will reflect parallel to the PA A ray towards C will reflect directly away from C. A ray towards C will reflect directly away from C. A ray to the intersection of PA and mirror will A ray to the intersection of PA and mirror will reflect at the same angle below the OA. reflect at the same angle below the OA. Trace the 3 diverging lines back through the mirror Trace the 3 diverging lines back through the mirror to reveal the location of the image which is always to reveal the location of the image which is always virtual virtual
13. 13. When a ray of light travels obliquely one medium to When a ray of light travels obliquely one medium to another, the direction of propagation of light in the another, the direction of propagation of light in the second medium changes. This phenomenon is second medium changes. This phenomenon is known as refraction of light. known as refraction of light.
14. 14. A good analogy for refracting light is a A good analogy for refracting light is a lawnmower traveling from the sidewalk lawnmower traveling from the sidewalk onto mud onto mud
15. 15. The speed of light is different in different media. The speed of light is different in different media. i.e., refraction is due to change in the speed of light i.e., refraction is due to change in the speed of light on going from one medium to another. on going from one medium to another.
16. 16. 1. The incident ray, the refracted ray and the normal to the 1. The incident ray, the refracted ray and the normal to the interface to two transparent media at the point of incidence, interface to two transparent media at the point of incidence, all lie in the same plane. all lie in the same plane. 2. The ratio of sine of angle of incidence to the sine of angle 2. The ratio of sine of angle of incidence to the sine of angle of refraction is a constant, for the light of a given colour of refraction is a constant, for the light of a given colour and for the given pair of media. This law is known as and for the given pair of media. This law is known as Snell's law of refraction. If the angle of incident and rr is the Snell's law of refraction. If the angle of incident and is the angle of refraction then, angle of refraction then, This constant value is called the refractive This constant value is called the refractive index of the second medium with respect to the first. index of the second medium with respect to the first.
17. 17. Converging Diverging f- curve of lens & index of refraction
18. 18. 1. Ray parallel to PA, refracts through far 1. Ray parallel to PA, refracts through far focal point focal point 2. Ray through center of lens, continues 2. Ray through center of lens, continues straight line straight line 3. Ray through near focal point, refracts 3. Ray through near focal point, refracts through lens, continues parallel to PA through lens, continues parallel to PA Treat lens as though it were a flat plane. Treat lens as though it were a flat plane.
19. 19. Diverging Lens Diagram • Because the rays that enter a diverging lens do not intersect a virtual image is formed by tracing back the refracted rays. • Ray 1 - parallel to PA, refracts away from near f, trace back to near f. • Ray 2 - ray toward far f, refracts parallel to PA, trace back parallel to PA • Ray 3 - ray through center, continues straight, trace back toward object
20. 20. Sign + – p q Near side of Far side of lens lens Far side of Near side of lens lens F Converging Lens Diverging Lens
21. 21. p = 30.0cm p = 30.0cm ff = 10.cm = 10.cm
22. 22. p = 12.5cm p = 12.5cm ff = -10.0cm = -10.0cm