If the radius of curvature of a convex lens is 20 cm, what is its focal length?

Practice Questions

Q1
If the radius of curvature of a convex lens is 20 cm, what is its focal length? (2022)
  1. 10 cm
  2. 20 cm
  3. 30 cm
  4. 40 cm

Questions & Step-by-Step Solutions

If the radius of curvature of a convex lens is 20 cm, what is its focal length? (2022)
  • Step 1: Understand that the radius of curvature (R) of a lens is the distance from the center of the lens to its surface.
  • Step 2: Know the formula for the focal length (f) of a convex lens, which is f = R / 2.
  • Step 3: Substitute the given radius of curvature (R = 20 cm) into the formula: f = 20 cm / 2.
  • Step 4: Perform the division: 20 cm divided by 2 equals 10 cm.
  • Step 5: Conclude that the focal length of the lens is 10 cm.
  • Lens Formula – The relationship between the radius of curvature and the focal length of a lens, specifically for thin lenses.
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