Question

You view your face in a concave mirror of focal length 20 cm and wish it to be magnified by a factor of 1.5. What should you do?

Answer 1

Answer:

u = 6.667 cm

Explanation:

given,

Focal length of the concave mirror, f = 20 cm

magnification factor = 1.5  

we know,

$M = \dfrac{-v}{u}$

v is the distance of the image

u is the distance of the object

$1.5 = \dfrac{-v}{u}$

v = -1.5 u

Using mirror formula

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

$\dfrac{1}{f}= \dfrac{1}{u} - \dfrac{1}{1.5u}$

$\dfrac{1}{20}=\dfrac{1}{3u}$

$3u = 20$

u = 6.667 cm

distance of the person from the mirror is equal to 6.667 cm.