Question

A` U`-shaped wire is placed before a concave mirror having radius of curvature `20 cm` as shown in figure. Find the total length of the image

Answer 1

Correct Answer - `116 cm`
For `AB`
`(1)/(v)+(1)/(u)=(2)/(R)`
`(1)/(v_(1))=(2)/(-20)+(1)/(15)=-(1)/(10)+(1)/(15)=(-3+2)/(30)=-(1)/(30)`
`v_(1)=-30`
`m_(1)=-(v)/(u)=-((-30))/(-15)=-2`
For `CD`
`(1)/(v)=(1)/(-10)+(1)/(20)=(-2+1)/(20)=-(1)/(20)`
`v=-20`
`m_(2)=-(v)/(u)=-((-20))/(-20)=-1`
`m_(2)=-1`
Total `=2+10+4=16 cm`