Question

After a check up, a person now has a far point of 100 cm, but with good near point vision. He needs to wear a new pair of corrective glasses. He accidentally takes his old contact lenses with him while traveling. If the lenses of the old pair have a power of -0.5 diopters, what is his far point (measured from his eye) when he is wearing the old lenses?

Answer 1

so his far point according to this pair of glass is 200 cm

Step-by-step explanation:

power of old pair of corrective glasses is given as

`P = -0.5 dioptre`

now we have

`f = (1)/(P)`

`f = -2 m`

`f = -200 cm`

now we know that for normal vision the maximum distance of vision is for infinite distance

so by lens formula we have

`(1)/(d_i) + (1)/(d_o) = (1)/(f)`

`(1)/(d_i) + 0 = (1)/(200)`

`d_i = 200 cm`

so his far point according to this pair of glass is 200 cm