Question

A magnifying glass is to be used at the fixed object distance of 1inch.if is to produce an erect image 5items magnified,focal length should be

Answer 1

u= -1 inch
v= ?
f=?
Since we do not have v we cannot apply the lens formula So first it is necessary to find image distance i.e., v.........


And because v is erect the sign convention of v would be in negative (-)


Also to mention that magnifying glass of convex lens



$m = \frac{v}{u}$
$v = - 1(5)$
v= -5 inches

Now apply the lens formula
$f= \frac{uv}{u - v}$
$= \frac{ - 1( - 5)}{ - 1 + 5}$
$\frac{5}{4}$
$\frac{5}{4} \times \frac{25}{25} = \frac{125}{100} = 1.25 \: inches$

Answer 2

Answer: 1.25

Explanation: