Question

An object of size 1cm placed at a distance of 20 cm in front of a convex lense of focal length 15 cm find the image distance size magnification and nature

Answer 1

lens formula, 1/F=1/v-1/u , here F= +15 cm , U= -20 cm Ho(height of the object)= 1cm, V=? , 1/15=1/V-(-1/20) , 1/15= 1/V+1/20 , 1/15-1/20=1/V , 4-3/60=1/V, 1/60=1/V, V= 60cm , m= V/U. m= 60/-20, m= -3 if m is negative means image form by convex lens is inverted and and it's value more than 1 means image is larger than object , inverted image is always real , we can also find Hi (height of the image) , m= Hi/Ho , -3= Hi/1, Hi= -3cm .