Question

Two lenses given focal lenght,height of object, Where its palced. Given everything but one variable solve for each variable. Make up a problem with made up values and show all equations used to solve for each variable like where is it place or how high it is ?

Answer 1

Two lenses given focal lenght,height of object.

so, for first lens 1/v1 -1/u1 = 1/f1

and for second lens use 1/v2- 1/u2 = 1/f2

here we consider two convex lens, whose focal length f is equal = + 30 cm given

for first case the object is at 60 cm from lens and so calculate the image distance for second lens where object will be at where image formed for first lens

so, for first lens: f1= +30 cm, u1 = - 60

so, 1/v1 -1/u1 = 1/f1

or, 1/v1 = 1/f1 + 1/u1 = 1/30 - 1/60 = 1/60

or, v1 = + 60 cm .......... image distance for first lens

so, for second lens: u2= v1 = - 60 cm and f2 = +30cm

1/v2 =  1/f1 + 1/u1 = 1/30 - 1/60 = 1/60

or, v2 = +60 cm

so image will be formed at 60 cm at right side of the lens