Laws of reflection:
(i) The incident ray, the reflected ray and the normal all three lie in the same plane.
(ii) The angle of incidence (i) is equal to the angle of reflection (r).
i.e., ∠i = ∠r.
Lenses |
Power (P) |
Aperture (A) |
L1 |
3D |
8 cm |
L2 |
6D |
1 cm |
L3 |
10D |
1 cm |
Presbyopia is a progressive form of far-sightedness that affects most people with ageing. The power of accomodation of the eye decreases.
Presbyopia arises due to the gradual weakening of the ciliary muscles and diminishing flexibility of the crystalline lens.
Simple reading eyeglasses with convex lenses correct most cases of presbyopia.