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Draw a ray diagram showing formation of image by a magnifying glass when the image is formed at infinity. Find the angular magnification of image. |
Answer» Solution : The RAY diagram has been shown in Fig. 9.48. As shown in FIGURE, the small object of linear SIZE h is placed at the focal plane of magnifying glass and its magnified image is formed at infinity. The object can subtend a maximum angle, when viewed directly without the lens, and be clearly visible when it is at near point of eye. The angle subtended by the object is then  `theta_(0) = tan theta_(0) = h/D` However, when SEEN through the lens, the object is placed at u = - f distance from eye. Hence, angle subtended by the image is same as angle subtended by object at distance u. THUS, `theta_(i) = tan theta_(i) = h/f` `therefore` Angular magnification `=theta_(1)/theta_(0) =(h//f)/(h//D)= D/f` |
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