Question

ᴀɴꜱᴡᴇʀ ᴛʜᴇ Qᴜᴇꜱᴛɪᴏɴ ɢɪᴠᴇɴ ɪɴ ᴛʜᴇ ᴀᴛᴛᴀᴄʜᴍᴇɴᴛ

Only relevant answers​

Answer 1

Answer:

(a) (i) The lens which can correct the vision of such a person suffering from both myopia and hypermetropia is a bifocal lens.

(ii) A common type of bifocal lens contains both concave and convex lens. It is prepared with the upper portion consisting of a concave lens facilitating distant vision and the lower portion consisting of convex lens facilitating near vision,

(b) The power for correcting his near vision,

P(N) = +3D

As P = 1 / f (m)

∵ Focal length of convex lens needed,

f(N) = 1 / P(N) = 0.33 m

= + 33.33 cm

Power required to correct distant vision, P(D) = -3D

∵ Focal length of concave lens,

f(D) = 1/ P(D) = -0.33 m

= -33.33 cm.

Answer 2

For near vision

p=1/f

f=1/p

=1/3

=0.33

For distant vision

p=1/f

f=1/p

=1/-3

=-0.33