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Two lenses of power - 15D and + 5D are i...

Two lenses of power - 15D and + 5D are in contact with each other. The focal length of the combination is .....

A

`+10 cm `

B

`-20 cm `

C

`-10 cm `

D

`+20 cm `

Text Solution

Verified by Experts

The correct Answer is:
A, C
Power of combination
`P=P_1+P_2`
`therefore 1/f=-15+5`
`therefore 1/f=-10`
`therefore f=-(1)/(10)` m
`therefore f=-(100)/(10) cm`
`therefore f=-10` cm
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KUMAR PRAKASHAN-RAY OPTICS AND OPTICAL INSTRUMENTS-SECTION-D (MULTIPLE CHOICE QUESTIONS (MCQs))(MCQs ASKED IN COMPETITIVE EXAMS)
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  13. A thin lens made of glass (refractive index = 1.5) of focal length f= ...

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