What is the image distance for a concave lens with a focal length of -12 cm when

Practice Questions

Q1
What is the image distance for a concave lens with a focal length of -12 cm when the object is placed at 24 cm?
  1. -8 cm
  2. 8 cm
  3. -12 cm
  4. 12 cm

Questions & Step-by-Step Solutions

What is the image distance for a concave lens with a focal length of -12 cm when the object is placed at 24 cm?
  • Step 1: Identify the given values. The focal length (f) of the concave lens is -12 cm, and the object distance (u) is 24 cm.
  • Step 2: Write down the lens formula: 1/f = 1/v - 1/u.
  • Step 3: Substitute the known values into the lens formula. Replace f with -12 cm and u with -24 cm: 1/(-12) = 1/v - 1/24.
  • Step 4: Simplify the equation. This gives: -1/12 = 1/v - 1/24.
  • Step 5: To isolate 1/v, add 1/24 to both sides: 1/v = -1/12 + 1/24.
  • Step 6: Find a common denominator to combine the fractions. The common denominator for 12 and 24 is 24.
  • Step 7: Rewrite -1/12 as -2/24. Now the equation is: 1/v = -2/24 + 1/24.
  • Step 8: Combine the fractions: 1/v = -2/24 + 1/24 = -1/24.
  • Step 9: Take the reciprocal to find v: v = -24 cm.
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