What is the power (in dioptres) of a convex lens of focal length ?
Answer and explanation
Correct answer: A. +5
- Step 1: The optical power of a lens in dioptres () is the reciprocal of its focal length measured in metres: .
- Step 2: Substitute the focal length (positive for a converging convex lens): .
Answer
+5.
Why not the others: omits the conversion from centimeters to meters; is the focal length in centimeters; and represents a diverging concave lens.
Practise more Science essentials.
Free questions with an explanation for every one, and full timed CBSE Class 10 mock tests.
More Science essentials questions
- Which gas is evolved when a metal reacts with a dilute acid?
- What is the pH of a neutral solution at 25 °C?
- Which type of lens is used to correct myopia (short-sightedness)?
- What is the SI unit of electric current?
- The reaction Fe + CuSO₄ → FeSO₄ + Cu is an example of a
- Which non-metal is a liquid at room temperature?