A concave lens has focal length of 20cm. At what distance from the lens a 5 cm tall object be placed so that it forms an image at a distance of 15 cm from the lens? Also calculate the size of the image formed.
Given,
Focal length of concave lens f = -20 cm
Height of object h1= 5 cm
Image distance v = -15 cm
Object distance u =???
Height of image h2 =???
We know that lens formula is:
Substituting the given values in the formula:
u = -60 cm
Substituting the value object height here
Height or size of the image = 1.25 cm
30