Below is a common instrument used in ophthalmology. In order to view the entire retina what is the power of lens you would like to attach to the instrument
Ans. (d) +20 DRef: Yanoff & Ducker 4/e, p. 89*Instrument is indirect ophthalmoscope.*Condensing lens commonly used is 20D biconvex lens.#Magnification=PoweroflensPowerofeye =20D60D =3times
+90 D
+78 D
-58 D
+20 D
Elementary Optics