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PRACTICE · MEMBERSIntermediate · Single correct

PRACTICE / Lens combinations

Combine positive and negative power

Lenses of power +5 D and −2 D are placed in contact in air.

Find the effective focal length.

Organize the givens & assumptions
  • P₁ = +5 D
  • P₂ = −2 D

Thin paraxial lenses in contact in air; negligible separation; signed optical powers.

  1. A+1/3 m+1/3\ \mathrm m
  2. B+1/7 m+1/7\ \mathrm m
  3. C−0.30 m-0.30\ \mathrm m
  4. D+3 m+3\ \mathrm m

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