If the focal length of a lens is 25 cm, what is the power of the lens?

Practice Questions

Q1
If the focal length of a lens is 25 cm, what is the power of the lens?
  1. +2 D
  2. +4 D
  3. +5 D
  4. +10 D

Questions & Step-by-Step Solutions

If the focal length of a lens is 25 cm, what is the power of the lens?
  • Step 1: Understand that the focal length of the lens is given as 25 cm.
  • Step 2: Convert the focal length from centimeters to meters. Since 1 cm = 0.01 m, we have 25 cm = 25 * 0.01 m = 0.25 m.
  • Step 3: Use the formula for power (P) of a lens, which is P = 1/f, where f is the focal length in meters.
  • Step 4: Substitute the focal length into the formula: P = 1/0.25 m.
  • Step 5: Calculate the power: P = 1/0.25 = 4 D (diopters).
  • Lens Power Calculation – The power of a lens is calculated using the formula P = 1/f, where f is the focal length in meters.
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