An older man finds he needs stronger reading glasses. After examination, it foun
ID: 1521898 • Letter: A
Question
An older man finds he needs stronger reading glasses. After examination, it found optimal to set his near point to 22cm in front his eyes. He is issued a prescription calling for lenses wih a power of 3.57 diopters for both eyes. Remember that the outgoing light is the light that leaves the lens and enters the eye. Explain the significance of the required power being positive rather than negative. Your response should be detailed and complete. Calculate how far away his near point ithout corrective lenses.
Explanation / Answer
In older ages people get affected by hypermetropia, which means that obejcts nearer to the eye are not seen clearly. To correct this problem the postive power lense is prescribed which is a diverging lense. (Concave lense)
In this case the near point is shifted to 22 cm , hence the older point can be calculated using the lense formula
1/f = 1/u - 1/v
f = 1/p = 28 cm
v = f *u /f - u = 28 *22/ 6 = 102 cm