Question

A 10 cm long pencil is placed 5 cm in front of a concave mirror having a radius of curvature of 40 cm.

1. Determine the position of the image formed by this mirror.
2. What is the size of the image?
3. Draw a ray diagram to show the formation of the image as mentioned in part (i).

Answer 1

`1/f = 1/v + 1/u`
where, u = −5 cm, f = `r/2 = -20` cm
`1/-20 = 1/v + 1/-5`

`= (-1)/20 = 1/5 + 1/v`

`(-1+4)/20 = 1/v = 3/20`

`v = 20/3 cm`

`m = (hi)/(ho) = (-v)/u`

`(hi)/10 = (-20/3)/-5`

`hi = 4/3xx10 = 40/3 cm`