A 10 mm long all pin is placed vertically in front of a concave mirror. A 5 mm long image of the all pin is formed at 30 cm in
front of the mirror. The focal length of this mirror is
(a) – 30 cm
(c) – 40 cm
(b) – 20 cm
(d) – 60 cm




So, the correct answer is (b)

  1. Class 10
  2. Chapter 10 Class 10 - Light - Reflection and Refraction (Term 1)

About the Author

CA Maninder Singh's photo - Founder at Teachoo
CA Maninder Singh
CA Maninder Singh is a Chartered Accountant for the past 11 years and a teacher from the past 11 years. He teaches Science, Accounts and English at Teachoo