A wire mesh consisting of very small squares is viewed at a distance of `8cm` through a magnifying converging lens of focal length `10 cm`, kept close to the eye. The magnification produced by the lens is:

Options

A. 8
B. 20
C. 10
D. 5

Answer

D

Explanation

Lens formula is given by
`(1)/(f)=(1)/(v)-(1)/(u)` ...(i)
where `f` is focal length of lens,` v` is image distance and `u` is object distance.
Given,` f=10cm` ( as lens is converging )
`u=-8cm` ( as object is placed on left side of the lens )
Substituting these values in Eq.(i), we get
`(1)/(10)=(1)/(v)-(1)/(-8)`
`implies(1)/(v)=(1)/(10)-(1)/(8)`
`implies (1)/(v)=(1)/(10)-(1)/(8)`
`:. v=(80)/(2)=-40cm`
Hence, magnification produced by lens
`m=(v)/(u)=(-40)/(-8)=5`