A person uses convex lens spectacles. What vision defect does he have? Draw a diagram 
(i) to show the defective eye
(ii) to show the correction with the lens.

25 How does the eye adjust its focal length? 26 Explain presbyopia and astigmatism. 28 How is the terrestrial telescope different from the astronomical telescope? 29 How will you distinguish between a compound microscope and a telescope.