You are given a concave mirror of focal length 50cm. How will you place an object in front of it, so that an image of double its size is obtained.
Sunil Bhardwaj
Solution: As we have a concave mirror focal length is negative, $$ \therefore f = -50 cm $$ and $$ Magnification (m) = \frac { v }{ u } = 2 $$ $$ \therefore v = 2u $$ By using mirror formula, $$ \frac { 1 }{ u } +\frac { 1 }{ v } =\frac { 1 }{ f } $$ Lets substitute the values, $$ \frac { 1 }{ u } +\frac { 1 }{ 2u } =\frac { 1 }{ -50 } \frac { 2+1 }{ 2u } $$ $$=\frac { -1 }{ 50 } \frac { 3 }{ 2u } $$ $$ =\frac { -1 }{ 50 } $$ $$ \therefore 2u = -\left( 3 \times 50 \right) $$ or $$ u = \frac { -150 }{ 2 } = -75 cm $$
Write your Comment
Please or to post comment!
No comments yet.
MCQ on Optics (Part 1)
500
400
MCQ on Optics (Part 2)
500
400
MCQ on Optics (Part 3)
500
400
MCQ on Optics (Part 4)
500
400
MCQ on Optics (Part 5)
500
400
Write a note on Charge.
500
400
