5.20 Thin Lenses in Combination

• When multiple lenses are used in series (one after the other) this is called a compound lens
• To find the total power of a compound lens, find the sum of the powers of the individual lenses

P_Total = P₁ + P₂ + .... P_n

• Where:
  • P_Total = Total power of all the lenses (dioptre, D)
  • P₁ = power of lens 1 (dioptre, D)
  • P₂  = power of lens 2 (dioptre, D)

• In this case the image is:
  • Virtual
  • Diminished
  • Upright

• The lenses should be:
  • Arranged so that their principle axes line up
  • Touching or very close