Question

Please anyone explain this step by step..I ak totally confused and did not understood anything..​

Answer 1

Solution:

According to the attachment,

• Concave mirror is given.
• Focal length, f = -15
• Object distance, u = -25
• Image distance, v = ???

Steps:

${\sf{:\implies \bigg(\dfrac{1}{f}\bigg) = \bigg(\dfrac{1}{u}\bigg) + \bigg(\dfrac{1}{v}\bigg)}}$

${\sf{:\implies \bigg(\dfrac{1}{-15}\bigg) = \bigg(\dfrac{1}{-25}\bigg) + \bigg(\dfrac{1}{v}\bigg)}}$

${\sf{:\implies \dfrac{1}{-15} = \dfrac{1}{-25} + \dfrac{1}{v}}}$

${\sf{:\implies \dfrac{1}{-15} + \dfrac{1}{25} = \dfrac{1}{v}}}$

LCM of 15 and 25 = 75!

${\sf{:\implies \dfrac{-5 \times 1 + 3 \times 1}{75} = \dfrac{1}{v}}}$

${\sf{:\implies \dfrac{-5 + 3}{75} = \dfrac{1}{v}}}$

${\sf{:\implies \dfrac{-2}{75} = \dfrac{1}{v}}}$

Cross multiplication!

${\sf{:\implies -2 \times v = 75 \times 1}}$

${\sf{:\implies -2v = 75}}$

${\sf{:\implies v \: = \dfrac{75}{-2}}}$

${\sf{:\implies v \: = -37.5}}$

• Henceforth, solved!

Hope it's helpful!