Example 9 12 a The near point of a hypermetropic person is

Last updated: 6/30/2023

Example 9 12 a The near point of a hypermetropic person is 75 cm from the eye What is the power of the lens required to enable the person to read clearly a book held at 25 cm from the eye b In what way does the corrective lens help the above person Does the lens magnify objects held near the eye c The above person prefers to remove the spectacles while looking at the sky Explain why Solution a u 25 cm v 75 cm 1 f 1 25 1 75 i e f 37 5 cm The corrective lens needs to have a converging power of 2 67 dioptres b The corrective lens produces a virtual image at 75 cm of an object at 25 cm The angular size of this image is the same as that of the object In this sense the lens does not magnify the object but merely brings the object to the near point of the hypermetric eye which then gets focussed on the retina However the angular size is greater than that of the same object at the near point 75 cm viewed without the spectacles c A hypermetropic eye may have normal far point i e it may have