Question

An object is placed 20 cm from a concave mirror and produces a real image 40 cm in front of the mirror. Use the mirror formula to

Answer 1

Answer:

Explanation:

Object distance = u = 20 cm

Image distance = v = 40 cm

Focal length = f  = ?

$Mirror Formula:- \\\\\dfrac{1}{f} = \dfrac{1}{v} + \dfrac{1}{u} \\\\= \dfrac{1}{f} = \dfrac{1}{( - 40)} + \dfrac{1}{( - 20)} \\\\= \dfrac{1}{f} = - \bigg \{ \dfrac{1}{ 40} + \dfrac{1}{20} \bigg \} \\\\= \dfrac{1}{f} = - \bigg \{ \dfrac{1 + 2}{ 40} \bigg \} \\\\= f = - \dfrac{40}{3} \\\\= f = - 13.33 \: cm$

Magnification is given as :

$mag. = - \dfrac{v}{u} = - \dfrac{ ( - 40)}{( - 20)} = - 2$

Negative magnification means that the image is inverted , real and magnified.