An object of size 3.0cm is placed 14cm in front of a concave lens of focal length 21cm. Describe the image produced by the lens. What happens if the object is moved further away from the lens?

Explanation

` (1)/(v)- (1)/( i) = ( 1)/( f) `
Substitution
Calculation of v `:`
`(1)/( v) = ( 1)/( v) - (1)/( (-14))`
`(1)/(v) = ( 1)/( 21) + ( 1)/( 14)`
`(1)/( v) = (5)/( 42)`
`v = 8.4 cm`
`m = ( "height of the image ")/( "height of the object") = ( - v)/( u ) `
`( h_(i))/( h_(0)) = ( -v)/(u)`
`( h _(i))/( 3) = ( -8.4)/( -14)`
`rArr h_(i) = ( 8.4 xx 3)/( 14)`
`h_(i) = 1.8cm`
Height of the image = 1.8 cm