Human eye defects
Tested in 2 real MPSC questions across 1 year (2018–2018). See it in context on the interactive Concept Graph →
Years it was asked
What you need to know first
Formula for optical powerUnits of dioptreSpherical lensesNear point of eye
Real questions that test this
ज्या व्यक्तीचे सुस्पष्ट दृष्टीचे लघुत्तम अंतर 50 cm आहे, अशा व्यक्तीच्या चष्माच्या भिंगांचे नाभीय अंतर किती असेल ? / What focal length should the spectacles have for a person for whom the least distance of distinct vision is 50 cm ?
1)50 cm, अंतरवक / 50 cm, concave
2)50 cm, बहिर्वर्क / 50 cm, convex✓ Correct
3)25 cm, अंतरवक / 25 cm, concave
4)25 cm, बहिर्वर्क / 25 cm, convex
For a person with least distance of distinct vision D = 50 cm (normal is 25 cm), a convex lens is used to correct hypermetropia. Using the lens formula with object distance u = -25 cm and image distance v = -50 cm gives a focal length of 50 cm.