Image formation by spherical mirrors:Concave Mirror
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Convex Mirror
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Magnification
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Uses of Spherical Mirrors:- Concave Mirror
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Convex Mirror
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Exercises
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What is mean by a spherical mirror??? Spherical mirrors are mirrors in which the reflecting surface is a part of the sphere. They are mainly of two types. Concave mirror and Convex mirror Concave mirror: Concave mirror is a mirror in which the reflecting surface is curved inwards Convex mirror: Convex mirrors are mirrors in which the reflecting surfaces are curved outwards.
Technical terms associated with spherical mirrors
1. Centre of curvature: Centre of a sphere of which the mirror is a part, is the centre of curvature of the mirror. In fig C indicates the centre of curvature. Any line drawn from the centre of curvature to the mirror is normal to the mirror.
2. Radius of curvature: Radius of curvature (R) of a mirror is the radius of the sphere of which it is a part. Distance from the centre of curvature to the reflecting surface of a mirror is the radius of curvature. In the figure, CP indicates the radius of curvature.
3. Aperture: Aperture of a mirror is the reflecting surface of the mirror.
4. Pole: Pole of a mirror is the midpoint of the reflecting surface of the mirror. It is represented as P in the figure.
5. Principal axis: Principal axis of a mirror is the straight line connecting the pole of the mirror and the centre of curvature of the mirror.
6. Principal focus: Rays of light incident on a concave mirror, parallel to the principal axis, passes through a fixed point on the principal axis after reflection. This point is the principal focus (F) of the concave mirror. The incident rays coming parallel to the principal axis after reflection appear to diverge from a common point on the principal axis, this point is called the principal focus of a convex mirror.
Concave mirror
Convex mirror
Image Formation by Spherical Mirrors Concave mirror
Click here to watch the video of image formation by a concave mirror. https://youtu.be/kNvcs_ARYVw
Convex mirror
Click here to see the video of image formation by a convex mirror. https://youtu .be/R2k8LAnz 17Ahttps
Magnification Magnification is the ratio of the height of the image to the height of the object. It is the number that indicates how many times size of the object is the size of the image. Magnification= hi/ho
While calculating the magnification, the measurement taken upwards from the principal axis is considered positive and the measurements downwards are considered negative. Magnification is a physical quantity having no unit.
Uses of Spherical Mirrors
Concave Mirrors
Shaving Mirror
Dental Mirror
Make up Mirror
Head Mirror
Convex Mirror
Used as reflectors in street lamps. Used as rear view mirrors by drivers for viewing vehicles from behind. These mirrors have a wide field of view compared to that of plane mirrors. Hence, they can help in avoiding accidents to a certain extent.
Exercises Write down the type of mirrors that should be used for getting the following type of images. a) Real and magnified b) Virtual and magnified c) Virtual and diminished d) Real and diminished The height of an object kept 12 cm away from a concave mirror is 1 cm. Calculate the magnification if an image of height 2.5 cm is formed in front of the mirror. Which type of mirror always gives a virtual and erect image? Is this image magnified or diminished? What are the difference between real and virtual images?