Question

A small candal, 2.5 cm in size is placed at 27 cm in front of a concave mirror of radius of curvature 36 cm. At wht distance from the mirror should a screen be placed in order to obtain a sharp image ? Describe the nature and size of the image. If the candale is moved closer to the mirror, how would the screen have to be moved ?

Answer 1

`u=-27cm, R = -36cm, f=-18cm`
`(1)/(u)+(1)/(upsilon)=(1)/(f)rArr(-1)/(27)+(1)/(v)=(-1)/(18)`
`(1)/(v)=(1)/(27)-(1)/(18) rArr (1)/(v)=(-1)/(54)`
`v=-54cm.`
The Screen should be placed 54 cm from the mirror
`m=(1)/(O)=(-v)/(u) rArr (I)/(2.5)=(-54)/(27)`
`U=-5cm`
`therefore` The image is real, inverted and magnified. If the candle is moved closer, the screen would have moved farther and farther. Closer than 18 cm from the mirror, the image gets virutal and cannot be collected on the screen.