Question

3 cm high object is placed 25 cm in front of a convex lens of focal length 15 cm. What is the position, nature and size of the image?

Answer 1

`"image distance:"37.5 " cm"`
`"image height: :"4.5" cm"`
`"please look at animation"`

Explanation:

`c:"height of object"`
`g:"image's height"`
`u:"object's distance from lens"`
`f:"focal length of object"`
`u^':"image's distance from lens"`

`"you can use the formula "1/f=1/u+1/u^'`

`"plug the given values into formula"`

`f=15" cm"`
`u=25 cm"`
`u^'=?`

`1/15=1/25+1/u^'`

`1/u^'=1/15-1/25`

`1/u^'=(5-3)/75`

`1/u^'=2/75`

`u^'=75/2`

`u^'=37.5" cm"`

`g/c=u^'/u`

`g/3=(37.5)/25`

`g=(3*37.5)/25`

`g=4.5" cm"`