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A person having a mypoic eye ueses a concave lens of focal length 50 cm. What is the power of the lens? |
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Answer» Here we have a concave lens. Now, the focal length of a concave lens is considered negative, so it is to be written with a minus sign. Thus, Focal length, f=`-50` cm `=-50/100` m `=-0.5` m Now, Power, P`=(1/("f in metres))` `P=1/-0.5` `P=(-1 x 10)/(5)` `P=-2` dioptres (or `-2`D) Thus, the power of this concave lens is, `-2` dioptres which can also be written as, `-2`D. The minus sign with the power indicates that it is diverging lens or concave lens. |
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