Magnification Formula
Magnification produced by a spherical mirror, the image of an object is magnified with respect to object size.
The magnification due to lens is the ratio of height of image (h’) to the height of the object (h). Magnification is denoted by M.
Magnification = Height of the image/Height of the object
M = h’/h —— (1)
The magnification due to lens is also related to the distance of object (u) and that of the image (v) from the lens.
Magnification (M) = h’/h = v/u —– (3)
Height of the object is taken to be positive the object is placed above the principal axis. The height of image is positive for virtual images & negative sign for real images.
If the value of magnification is negative then image is real and value of magnification is positive then image is virtual.
Numericals on Magnification Formula:
(1) Find the magnification? If the image distance is 16 cm in front of mirror and object distance is 6 cm in front of mirror.
Given:
Object distance = u = -6
Image distance = v = -16
-ve sign because of they are in front — mirror.
M = -v/u
M = (-16)/(-6)
M = -16/6
M = 2.66
(2) The focal length of concave mirror is 20 cm and object of size 8 cm placed at 40 cm in front of concave mirror. Find the distance from the mirror should screen be placed in order to obtained a image? Find size of image and nature?