If the radius of curvature of a lens is 30 cm and the refractive index is 1.5, w

Practice Questions

Q1
If the radius of curvature of a lens is 30 cm and the refractive index is 1.5, what is the focal length of the lens?
  1. 10 cm
  2. 15 cm
  3. 20 cm
  4. 25 cm

Questions & Step-by-Step Solutions

If the radius of curvature of a lens is 30 cm and the refractive index is 1.5, what is the focal length of the lens?
  • Step 1: Identify the given values. The radius of curvature (R) is 30 cm and the refractive index (n) is 1.5.
  • Step 2: Write down the lens maker's formula: f = R / (n - 1).
  • Step 3: Substitute the values into the formula: f = 30 / (1.5 - 1).
  • Step 4: Calculate the value inside the parentheses: 1.5 - 1 = 0.5.
  • Step 5: Substitute this value back into the formula: f = 30 / 0.5.
  • Step 6: Perform the division: 30 divided by 0.5 equals 60.
  • Step 7: Conclude that the focal length (f) of the lens is 60 cm.
  • Lens Maker's Formula – The formula used to calculate the focal length of a lens based on its radius of curvature and refractive index.
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