Ray Optics — Easy JEE physics MCQ
An object is placed $20$ cm from a concave mirror of focal length $10$ cm. The image distance is:
- A. $20$ cm
- B. $10$ cm
- C. $40$ cm
- D. $5$ cm
Solution
$\frac{1}{f} = \frac{1}{v} + \frac{1}{u}$
$\frac{1}{-10} = \frac{1}{v} + \frac{1}{-20}$
$\frac{1}{v} = -\frac{1}{10} + \frac{1}{20} = -\frac{1}{20}$
$v = -20$ cm (real image, 20 cm in front)