Two lenses of power 15D and -3D are placed in contact. The focal length of the combination is aA. 10cmB. 15cmC. 12cmD. 18cm

Two lenses of power 15D and -3D are placed in contact. The focal lengt

1.	Two lenses of power 15D and -3D are placed in contact. The focal length of the combination is aA. 10cmB. 15cmC. 12cmD. 18cm
Answer» Correct Answer - D `"Given" P_(1)=15D and P_(2)=-3D` `therefore P=P_(1)+P_(2)=15D-3D=12D ` `therefore P=(1)/(f(m)) Rightarrow P=(100)/(f(cm)) Rightarrow 12=(100)/(f)` Focal length of the combination, `f=(100)/(12)=8.33cm`

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Two lenses of power 15D and -3D are placed in contact. The focal length of the combination is aA. 10cmB. 15cmC. 12cmD. 18cm

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