An object is placed at a distance of 30 cm from a concave lens of focal length 30 cm.
(i) Use lens formula to determine the distance of the image from the lens.
(ii) List four characteristics of the image (nature position, size, erect/inverted) in this case.
(iii) Draw a labelled diagram to justify your answer of part (ii).

Explanation

Object distance, `u= -30 cm,` Focal length, `f = -30 cm`
(i) Lens formula, `1/f = 1/v - 1/u`
So `1/v = 1/f+1/u rArr 1/v= 1/-30+1/-30 =(1+1)/-30 = 2/-30`
`v= -15 cm`
The image distance is 15 cm in front of the lens.
(ii) Characteristics of image formed. The image is -
`*`virtual, " " `*` erect, " "`*`diminished,
`*` in front of the lens between 'O' and 'F', and
`*` 15 cm from the lens on the same side as the object
(iii)