Question

Which of the following is the correct lens formula?

• A. $ \frac{1}{v}- \frac{1}{u} = \frac{1}{f}$
• B. $ \frac{1}{v}+ \frac{1}{u} = \frac{1}{f}$
• C. $v - u = f$
• D. $v + u = f$

Answer 1

Answer: (A)

The lens formula is given as $\frac{1}{f} = \frac{1}{v} - \frac{1}{u}$, where $f$ - focal length, $u$- object distance from the lens and $v$- image distance from the lens. The lens formula is implemented with proper sign convention using cartesian method.