Question

Power is - 25 D.
OR
A person suffering from myopia (near-sightedness) was advised
wear corrective lens of power - 2.5 D. A spherical lens of same
focal length was taken in the laboratory. At what distance should a
student place an object from this lens so that it forms an image at
a distance of 10 cm from the lens ?​

Answer 1

ANSWER:-

Power of a lense = 1/its focal length

P=1/f

f=1/p

f=1/2.5

f=0.4 m. =>. f=40 cm

According to lens formula

1/f=1/v–1/u

1/40=1/10–1/u

1/u= 1/10–1/40

1/u= 40–10/400

1/u=30/400

1/u=3/40

u= 40/3

u=13.33cm

So, the object should be at the distance of 13.33 cm from the lens.....

HOPE THIS WILL HELP YOU!!!!!

Answer 2

Answer: The answer is -13.33

Explanation: The previous answer is wrong since in concave the focal length, image distance and object distance is always negative.