Question

5. For a Concave mirror, it the
Size of object is 4 cm and size
of image is 3cm
what is the magnification?
b) If the distance between pole and
Image is 8 cm ? what is distance
pole
and object ?​

Answer 1

Given :

height of object, h = 4 cm

height of image, h' = 3 cm

image distance, v = - 8cm

Remember !

In concave mirror image distance is negative because the image is formed left side of mirror

To find :

a) Magnification

b) object distance

Solution :

a) The ratio of the height of image to the height of object is known as magnification.

${ \leadsto{ \bf{Magnification = \dfrac{h'}{h}}}}$

here, h' denotes image height and h denotes object height.

${ \leadsto{ \bf{m = \dfrac{4}{3}}}}$

${ \leadsto{ \bf{m = 1.3}}}$

thus magnification is 1.3

b) the linear magnification produced by a mirror is equal to the ratio of the image distance to the object distance, with a minus sign .i.e.,

${ \leadsto{ \bf{Magnification = - \dfrac{v}{u}}}}$

here, v denotes image distance and u denotes object distance.

${ \leadsto{ \bf{1.3 = - \dfrac{ - 8}{ \: u} }}}$

${ \leadsto{ \bf{u = \dfrac{8}{1.3} }}}$

${ \leadsto{ \bf{u = 6.1 \: cm \: (approx)}}}$

thus, the distance between the pole and the object is 6.1 cm (approx)