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Two lenses of local lengths 0.20m and 0.30m are kept in contact. Find the focal length of the combination. Calculate power of two and combination. |
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Answer» Solution :Here: `f_1=0.20m,f_2=0.30m,f=?, P_(1)=?,P_(2)=?,P=?` The effective focal length of the combination is `1/f=1/(f_(1) ) + 1/(f_2)` `= (1)/(0.20) + 1/(0.30)` f = 0.12 m POWER of LENS is P = 1/f `P_(1) = 1/f_(1) = 1/(0.20) = 5D` `P_(2) = 1/f_(2) = 1/(0.30) = 3.333D` `P = 1/f = 1/(0.12) = 8.333 D` `P = P_(1) +P_2` `= 5 + 3.333` `= 8.333` D |
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