Question

A far sighted person can see object beyond 71cm clearly if separation between glasses and eye lenses is 2cm, find focal length of glass???

Answer 1

Answer:

The answer will be 69 cm

Explanation:

According to the problem the person can see more  than 71 cm

Therefore if we take distance between the image and the glass is v

Therefore v = 71cm = 0.71m

It is mentioned that the distance between glass and eye is 2 cm = 0.02m

Therefore the distance between eye to image - 0.71-0.02 = 0.69m

Now let the focal lenght of the glass be f

Theresore v = -0.69m and u is infinity

Therefore

1/f = 1/v- 1/u = 1/-0.69 = 0.69

Therefore the focal length will be 69 cm