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Obtain the magnification for the image form at infinity for simple microscope. |
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Answer» SOLUTION :Suppose the object has a height h the MAXIMUM angle it can subtend and be clearly visible. (without a lens) is when it is at the near POINT i.e., a distance D. `tan theta_0=h/D` For small angle, `tan theta_0 ~~ theta_0` `therefore theta_0=h/D` ...(1)  Now if the angle subtended at the eye by the image when the object is at u `theta_i`, then `tan theta_i=h/f` For small angle, `tan theta_i~~theta_i` `therefore theta_i=h/f` ...(2)  From the figure angular magnification, `m=(theta_i)/(theta_0)` From EQUATION (1) and (2), `m=(h//f)/(h//D)` `therefore m=D/f` This is one less than the magnification when the image is at the near point but the viewing is more comfortable and the difference in magnification is usually small. The maximum limited magnification is (`le 9`) for real focal lengths for simple microscope. |
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