At what distance should an object be placed from alens of focal length 25 cm to obtain an image on a screen placed at a distance of 50 cm from the lens ? What will be the magnification produced in this case?

At what distance should an object be placed from alens of focal length

1.	At what distance should an object be placed from alens of focal length 25 cm to obtain an image on a screen placed at a distance of 50 cm from the lens ? What will be the magnification produced in this case?
Answer» Solution :Given: Focal length (f)=25 cm image distance (v)=50 cm To find: Object distance (U) FORMULA: `(1)/(f)=(1)/(v)-(1)/(u)` CALCULATION: From formula, `(1)/(25)=(1)/(250)-(1)/(u)` `therefore" "(1)/(u)=(1)/(50)-(1)/(25)=-(1)/(50)` `therefore" "u=-50 cm` The NEGATIVE SIGN indicates that object is placed on left of the lens.