(a) A student has focussed the image of an object of height 3 cm on a white screen using a concave mirror of…
(a) A student has focussed the image of an object of height 3 cm on a white screen using a concave mirror of focal length 12 cm. If the distance of the object from the mirror is 18 cm, find the values of the following :
(i) Distance of the image from the mirror
(ii) Height of the image
Solution
(a) Here h = 3 cm; f = – 12 cm, u = - 18 cm,
(Award full marks if data not written but calculations are correct)
(i)
v = ?, h' = ?
$\dfrac{1}{f}$ = $\dfrac{1}{v}$ + $\dfrac{1}{u} \dfrac{1}{v}$ = $\dfrac{1}{f}$ - $\dfrac{1}{u}$ = 1/(-12 cm) - 1/(-18 cm)
∴ v = – 36 cm
(ii)
h' = -v/u × h
h' = (-) (-36cm / -18cm) × 3 cm = – 6 cm