Question

ii) Name two optical instrument
iii) List three characteristics of the image formed if this lens is replaced
by a concave mirror of focal length 'f and an object is placed at a
distance 'f/2 in front of the mirror.​

Answer 1

Given that,

(ii). Name two optical instrument

(a). Microscope

(b). Telescope

(iii). If this lens is replaced  by a concave mirror

Focal length = f

Object distance = f/2

We need to calculate the image distance

Using formula of mirror

$\dfrac{1}{f}=\dfrac{1}{v}+\dfrac{1}{u}$

Where, f = focal length

u = object distance

v = image distance

Put the value into the formula

$\dfrac{1}{-f}=\dfrac{1}{v}-\dfrac{2}{f}$

$\dfrac{1}{v}=\dfrac{1}{-f}+\dfrac{2}{f}$

$\dfrac{1}{v}=\dfrac{1}{f}$

$v=f$

The image distance is equal to the focal distance from the mirror.

Hence, (ii). (a). Microscope

(b). Telescope.

(iii). Characteristic of the image

(a). The image is formed behind the mirror.

(b). The image is virtual.

(c). The image is magnified.