500度近視鏡放大率即是多少- @ gpjqem1的部落格

標題:

500度近視鏡放大率即是多少?

發問:

500度近視鏡放大率即是多少?500度近視鏡的放大率/縮小率是否即是0.5x?謝謝.

最佳解答:

500 degrees of short sightedness = -5 dioptres where dioptre is a unit for the refractive power of a concave/convex lens By definition of dioptre, focal length of lens (in metre) = 1/dioptre hence, focal length of concave lens required for 500 degrees of short sight = -1/5 m = -0.2 m The image distance v formed by one such lens for an object placed at the distance of distinct vision D (=25 cm, or 0.25 m), using the thin lens formula, is 1/D + 1/v = -1/0.2 1/v = -1/0.2 - 1/0.25 m^-1 = -9 m^-1 v = -1/9 m = -0.111 Magnification = v/D = 0.111/0.25 = 0.44