A person cannot see the objects beyond 40 cm the power of the lens to correct this vision will be

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58.A person cannot see any object clearly beyond 40 cm distance from eye. Find the focal length and power of lens he needs in his spectacles for normal vision.

Solution

Text Solution

Solution : The person cannot see objects clearly beyond 0.4m, so his far point =0.4m distance of object=a <br> He should use lens which forms image of distant object at a distance of 40 cm infront of it. <br> `-1/0.40-1/-infty=1/f=p implies P=(-10)/4=-2.5D`