a convex lens produces an inverted image magnified three times of an o

1.	a convex lens produces an inverted image magnified three times of an object placed at a 15cm from it. calculate the focal length of the lens.
Answer» <U>Answer: FOCAL length of lens is +11.25 cm. Step-by-step explanation- Given: m ( MAGNIFICATION ) = -3 [ Since the image is inverted, magnification will be -3] u ( object distance ) = -15cm To find: focal length = ? ____.. We know that ${\boxed {\huge {\tt m= \frac{<klux>V</klux>}{u}}}}$ Where, m is magnification v is image distance u is object distance $\tt {\implies - 3 = \frac{v}{ - 15}}$ $\tt {\implies v = ( - 3 )\times ( - 15)}$ $\tt\blue {\implies v = 45cm}$ Now, ACCORDING to lens formula- ${\boxed {\huge {\tt \frac{1}{v} - \frac{1}{u} = \frac{1}{f}}}}$ Substituting values- $\tt { \longrightarrow \frac{1}{45} - \frac{1}{ -15} = \frac{1}{f} }$ $\tt { \longrightarrow \frac{1 + 3}{45} = \frac{1}{f}}$ $\tt { \longrightarrow \frac{4}{45} = \frac{1}{f}}$ $\tt\red { \longrightarrow f = \frac{45}{4}}$ [ After reciprocating both sides] $\tt\red { \longrightarrow f = 11.25}$ Hence, the focal length of the lens is 11.25 cm.