Question

An object O is placed at a point distance x from the focus $F_1$ of a convex lens of focal length f (both side medium being same) and its image I is formed at a distance $x^{\prime }$ from $F_2$ as shown in the figure. the magnification is

• A. $\frac{f}{{x+x}^{{}^{\prime }}}$
• B. $\frac{x^{{}^{\prime }}}{x}$
• C. $\frac{f}{x}$
• D. none of these

Answer 1

Answer: (D)

none of these

$\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$

$\frac{1}{x^{‘}}-\frac{1}{x}=\frac{1}{f}$

$\frac{1}{x^{‘}}=\frac{1}{x}+\frac{1}{f}$

$\frac{1}{x^{‘}}=\frac{x+f}{xf}$

$x^{‘}=\frac{xf}{x+f}$

magnification $=\frac{-v}{u}=\frac{-x^{‘}}{x}=\frac{f}{x+f}$

option 'D' is correct.