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LIGHT A LIGHT IS A FORM OF ENERGY WHICH PRODUCES IN US THE SENSATION OF SIGHT. WE CAN SEE OBJECTS BECAUSE OF LIGHT.

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The Law of Reflection Angle of incidence = Angle of reflection The same !!! Incident ray Reflected ray Mirror Normal

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N 1 N 2 Eye A Refracting Surfaces Prism i e REFRACTION OF LIGHT THROUGH A TRIANGULAR PRISM - Activity Q P S R

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The twinkling of a star is due to atmospheric refraction of starlight. Since the atmosphere bends starlight towards the normal, the apparent position of the star is slightly different from its actual position. The star appears slightly higher (above) than its actual position when viewed near the horizon. Eye LAYERS OF ATMOSPHERE Apparent position of the Star Real position of the Star TWINKLING OF STARS

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Advance Sunrise and Delayed Sunset: The Sun is visible to us about 2 minutes before the actual sunrise, and about 2 minutes after the actual sunset because of atmospheric refraction. Earth Atmosphere Horizon Apparent position of the Sun Real position of the Sun

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DISPERSION OF WHITE LIGHT THROUGH A PRISM The phenomenon of splitting a ray of white light into its constituent c o l o u r s (wavelengths) is called dispersion and the band of colours from violet to red is called spectrum ( V I B G Y O R ). A B C White light R O Y G B I V Screen N

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PARTS OF A SPHERICAL MIRROR 1.Radius of curvature =The radius of curvature of a spherical mirror is the radius of a hollow glass from which it is detached. 2.Aperture =The portion of mirror from which the reflection of light actually takes place is called aperture. 3.Pole =The center part of the mirror is called pole. 4.Principal axis =The principal axis of a spherical mirror is the straight line passing through the center of curvature C and pole P of the spherical mirror,produced on both sides.

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Concave Mirror A Concave mirror is a spherical mirror in which reflection of light takes place at the bent in surface.It is also known as converging mirror.

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CONVEX MIRROR A Convex mirror is that spherical mirror in which the reflection of light take place at the blurging out surface.it is also known as diverging mirror.

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Rules for tracing images formed by spherical mirror 1. An incident ray parallel to the principal axis will always pass through the focus. F P C Concave mirror F P C Convex mirror

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RULES 2. An incident ray passing through the focus will emerge parellel to principal axis. C F P Concave mirror P C F Convex mirror

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RULES 3.The incident ray passing through the center of curvature will return back on the same path. C Convex mirror C Concave mirror

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RULES 4. A ray incident towards pole reflected making equal angles with the principal axis Convex mirror Concave mirror i i r r

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Formation of image by concave mirror When an object is at a very large distance from a concave mirror, it is said to be at infinity.such an object cannot be shown in the diagram.When the object is at infinity,the image will always be formed on the focus and the image will be real and inverted and highly diminished. 1. When the object is at infinity. F C P

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2.When the object is beyond the curvature= When the object is beyond the curvature, the image is located between center of curvature and focus, and the image will be real,inverted and diminished. Formation of image by concave mirror C F o i

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3.When the object is at the center of curvature When the object is at the center of curvature,the image will formed at the center of curvature and the image will be of same size,real and inverted. Formation of image by concave mirror C F

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4. When the object lies between center of curvature and focus = When the object lies between center of curvature and focus, the image will formed beyond the center of curvature and will be real, inverted and enlarged. Formation of image by concave mirror C F

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5. When the object is at the focus When the object is placed at the focus its image will formed at infinity and image will be real, inverted and enlarged. Formation of image by concave mirror C F Image is formed at infinity o

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6. When the object is between focus and pole When the object is between focus and pole,the image will formed behind the mirror and the image is virtual and erect. Formation of image by concave mirror C F o image

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IMAGE FORMATION BY CONVEX MIRROR When the object is at infinity when the object is placed at infinity the image will appear at focus and the image will be virtual erect and highly diminished. F C PRINCIPAL AXIS i

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IMAGE FORMATION BY CONVEX MIRROR 2. When the object is at finite distance when the object is places at the finite distance its image will formed between pole and focus .it wil be virtual , erect and diminished. C F

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