SUBMITTED BYMUBASHIRA M
LIGHT - REFLECTION
Reflection of lightThe process of sending back the light rays which falls on the surface of an object Reflection The object having polished , shining surface reflects more light than object having unpolished, dull surface
Silver metal is good reflector of light
Laws of reflection of lightThe incident ray , the normal to the mirror at the point of incidence and the reflected ray , all lie in the same plane.
The angle of incidence is equal to the angle of reflection.
It is a mirror which has the shape of a piece cut out of a spherical surfaceSpherical mirror
Concave mirror It is a spherical mirror , whose reflecting surface is curved inward or faces towards the centre of the sphere.
CONVEX MIRROR It is a spherical mirror whose reflecting surface is curved outward
Types of spherical mirror
Pole (p) centre point of the reflecting surface of a spherical mirror. It lies on the surface of the mirror.
Centre of curvature (C)- Centre point of the sphere , in which the reflecting surface of a spherical mirror forms a part of this sphere
Radius of curvature (R)- the radius of the sphere of which the reflecting surface of a spherical mirror forms a part.
Principal axis Is a straight line passing through the pole and the centre of curvature of a spherical mirror.
Aperture- the diameter of the reflecting surface of spherical mirror Terms of reflection
Focal length the distance between the pole and the principal focus of a spherical mirror
A number of ray parallel to the principal axis are falling on a concave mirror and the reflected rays are all intersecting at a point on the principal axis of the mirror. This point is called the Principal focus of the concave mirror
Principal focus of the convex mirror the reflected rays appear to come from a point on the principal axisPrincipal focus and Focal length
Rays of light coming from infinity, making different angles with the principal axis get focused at different points.
The plane formed by these points is perpendicular to the principal axis and passes through the principal focus.
This plane is the principal axis
For a spherical mirror of small aperture,
The principal focus F lies midway - between the pole P and the centre of curvature C
The radius of curvature is found to be equal to twice the focal length
R = 2f
Ray diagram of spherical mirror Path of incident ray Path of reflected ray Concave mirror Convex mirrorParallel to the principal axis Reflect through the focusAppears to come from the principal focus Through the principal focus/ in the direction of the principal focus Reflects parallel to the principal axis Reflects parallel to the principal axis Through the centre of curvature/ in the direction of centre of curvature Reflects through the same pathReflects through the same path Ray falling obliquely at the pole Reflects in such a way that the angle of incidence equal to the angle of reflectionReflects in such a way that the angle of incidence equal to angle of reflection
Image formation by a Concave mirror for different position of the ObjectPosition of the objectPosition of the imageSize of the imageNature of the imageAt infinityAt the focus FHighly diminished, point sizedReal and invertedBeyond CBetween F and CdiminishedReal and invertedAt CAt C Same sizeReal and invertedBetween C and FBeyond CEnlargedReal and enlargedAt F At infinityHighly enlargedReal and enlargedBetween P and FBehind the mirrorEnlargedVirtual and erect
Ray diagrams for the image formation by a concave mirror
Between P and F At F Between C and F At C Beyond C At infinity
Commonly used in torches, search lights
Vehicle headlights to get powerful parallel beams of light
Often used as shaving mirror to see large image of the face
Dentists use concave mirror to see large images of the teeth of patients
large concave mirrors are used to concentrate sunlight to produce heat in solar furnace Uses of concave mirror
Image formation by a Convex mirrorPosition of the objectPosition of the imageSize of the imageNature of the image At infinityAt the focus F, behind the mirrorHighly diminished, point sizedVirtual and erectBetween infinity and the pole P of the mirrorBetween P and F, behind the mirrorDiminishedVirtual and erect
Commonly used as rear-view mirror in vehicles, because
Enabling the driver to see traffic behind him to facilitate safe driving
They always give an erect, though diminished image
View as they are curved outward
Enable the driver to view much larger area than would be possible with a plane mirror Uses of Convex mirror
Real image Virtual image Inverted Virtual Can be formed on the screen Cannot be formed on a screen The distance towards the image and its height can be measured directly The distance towards the image and its height cannot be measured directly
Real image Vs Virtual image
It is expressed as the ratio of the height of the image to the height of the object
It is usually represented by the letter
Magnification produced by a spherical mirror gives the relative extent to which the image of an object is magnified with respect to the object size
m = Height of the image / Height of the object
Magnificationm = h/h m
Magnification m is also related to the object distance (u ) and image distance (v)
Object is taken to be positive as the object is usually placed above the principal axis
Height of the image should be taken as positive for virtual images, however taken as negative for real images
A negative sign in the value of the magnification indicates that the image is real
A positive sign in the value of the magnification indicates that the image is virtual Magnification (m) = h/h = - v/ u