Mirror Formula and Linear magnification produced by Mirror
Definition of Mirror Formula :
A formula which gives the relationship between image distance (v) , object distance (u) and focal length (f) of a spherical mirror is known as the mirror formula.
Mirror Formula: 1/f = 1/u + 1/v
Where f is focal length of the mirror
u is distance of object from mirror
v is distance of image from mirror
Defination of Linear Magnification:
The ratio of the height of image to the height of object is known as Linear Magnification
m = h2/h1= height of image / height of object
Linear Magnification produced by a mirror is equal to the ratio of the image distance to the object distance , with a minus sign.
Magnification m = -v/u = -Image distance / Object distance
m = -v/u = h2/h1
- If the magnification has a plus sign +m then the image is virtual and Eract.
- If the magnification has a minus sign -m, then the image is real and inverted.
- Concave mirror can be less than m< 1 , equal to m= 1 or more than m>1.
- Convex mirror forms images which are smaller than the object. m<1.
- Height of the object will always be positive.
- Height of virtual image will be positive.
- Height of real image will be negative.
- A plane mirror forms image which are always of the same size as the object , therefore the magnification (m) produced by a plane mirror is always 1 , m= 1