PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Geometrical optics and imaging · Geometrical optics and imaging
Optics and Photonics, Ch Stops, pupils and optical instruments
Problem
Three short calculations, all with thin lenses, paraxial rays and the standard near point d0=250 mm where it is needed.
((a)) A long-sighted reader's near point is at 800 mm. What power (in dioptres) must a thin spectacle lens have so that a page held 250 mm from the lens is imaged at the reader's near point, 800 mm in front of the lens? Use the book's convention: a virtual image lies on the object side and has si<0.
((b)) A converging lens of focal length 50 mm is used as a simple magnifier with the eye relaxed (final image at infinity). Give its angular magnification, with the unaided angle taken at d0=250 mm.
((c)) A compound microscope has a tube length L=160 mm (objective focal point to eyepiece focal point), an objective of focal length fo=8 mm and an eyepiece of focal length fe=20 mm used relaxed. Give the overall magnification, including its sign.