Question

an object was placed on the principle axis of a convex lense 25cm away from the lense a real image 4 time the size of the object was obtained the focal length of lesne​

Answer 1

From the figure,

u=−(25+f)

v=(40+f)

Using lens formula we get

v1 − u1 = f1

f+401 + 25+f1 = f1

65f+2f=1000+65f+f2

f 2=1000

f=31.623cm

∴u=25+31.62=56.62cm

v=40+31.623=71.62cm

m= uv

= −56.62 +71.62

= −1.3

Answer :- -1.3