6. The power of a lens is expressed in diopters (D). You have probably seen this

Question

6. The power of a lens is expressed in diopters (D). You have probably seen this used in eyeglass prescriptions where converging lenses (reading glasses) are prescribed in positive diopters and diverging lenses (correction for near sightedness) are prescribed using negative diopters. The power, in diopters, is obtained by taking the inverse of the focal length, after the focal length is converted to meters. The power of two or more adjacent lenses is simply the sum of their individual powers. D = D1 + D2 + ?+ Dn Find the combined power of three close-up lenses for a camera that are rated +1D, +2D, and +3D. What is the focal length of each lens? What is the focal length of the stack of three lenses?

Explanation / Answer

combined power will be simply = 1D +2D +3D = 6D

1 dioptre = i/f = f=1m=100cm

similarly 2 D= 1/f

=> f= 1/2 m =0.5 metre=50cm

3 dioptre = 1/f = f=1/3 = 0.33 metre =33.33 cm

finally for the 6D ,

focal lngth = 1/6 metre= 0.1666metre = 16.66 cm

Related Questions

Navigate

• Browse (All)
• Browse 6
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.