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Physics - Geometrical Optics Question with Solution | TestHub

PhysicsGeometrical OpticsRefraction+ReflectionEasy2 minPYQ_2019

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A convex lens of focal length ‘f’ is placed in contact with a concave lens of the same focal length. The equivalent focal length of the combination is

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Answer:

Solution:

Given, focal length of convex lens, $f_{1} = f$
and focal length of concave lens, $f_{2} = - f$ .
The focal length of combination, when two lenses are in contact is given by
$\frac{1}{f} = \frac{1}{f_{1}} + \frac{1}{f_{2}}$
Substituting given value in Eq. (i). We get
$\Rightarrow \frac{1}{f} = \frac{1}{f} - \frac{1}{f} = 0 \Rightarrow f = \infty$
Hence, the equivalent focal length of the combination is infinity.

Stream:MHT_CETSubject:PhysicsTopic:Geometrical OpticsSubtopic:Refraction+Reflection

⏱ 2mℹ️ Source: PYQ_2019

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