Certain people wear bifocal glasses to improve their near and far vision. Part A
ID: 1398616 • Letter: C
Question
Certain people wear bifocal glasses to improve their near and far vision.
Part A
If a person can only see things clearly from a distance of 50.5 cm to 90.0 cm from his eyes without glasses, what powers of bifocal glasses should she wear so she can see things clearly from 25.0 cm to infinity?
Plower,Pupper = ? D
Certain people wear bifocal glasses to improve their near and far vision.
Part A
If a person can only see things clearly from a distance of 50.5 cm to 90.0 cm from his eyes without glasses, what powers of bifocal glasses should she wear so she can see things clearly from 25.0 cm to infinity?
Plower,Pupper = ? D
Explanation / Answer
Given that ::
Punctum Proximum, PP = 50.5 cm
Punctum Remotum, PR = 90 cm
Powers of bifocal glasses where she should wear & can see things clearly from 25 cm to infinity is given as ::
Pupper = -1 / PR { eq.1 }
inserting the values in above eq.
Pupper = -1 / (90 cm) = - (100) / (90 m)
Pupper = - 1.11 D
and
Plower = 4 - (1 / PP) { eq.2 }
inserting the value of 'PP' in eq.2,
Plower = 4 - (1 / 50.5 cm)
Plower = 4 - (100 / 50.5 m)
Plower = (4 - 1.98) D
Plower = 2.02 D