A convex lens has a focal length of 15 cm. What is the power of the lens?

Practice Questions

Q1
A convex lens has a focal length of 15 cm. What is the power of the lens?
  1. +6.67 D
  2. +7.5 D
  3. +10 D
  4. +15 D

Questions & Step-by-Step Solutions

A convex lens has a focal length of 15 cm. What is the power of the lens?
  • Step 1: Understand that the power of a lens is calculated using the formula P = 1/f, where P is the power in diopters (D) and f is the focal length in meters.
  • Step 2: Convert the focal length from centimeters to meters. Since the focal length is given as 15 cm, divide by 100 to convert it to meters: 15 cm = 15/100 = 0.15 m.
  • Step 3: Substitute the focal length in meters into the power formula. So, P = 1/0.15.
  • Step 4: Calculate the value of P. When you divide 1 by 0.15, you get approximately 6.67.
  • Step 5: Since the lens is convex, the power is positive. Therefore, the final answer is +6.67 D.
  • Lens Formula – Understanding the relationship between focal length and power of a lens.
  • Unit Conversion – Converting focal length from centimeters to meters to calculate power.
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