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Physics - Geometrical Optics Question with Solution | TestHub

PhysicsGeometrical OpticsRefraction at curved surface/LensEasy2 minPYQ_2020

PhysicsEasysingle choice

Two thin equiconvex lenses each of focal length $0.2 m$ are placed coaxially with their optic centres $0.5 m$ apart. Then the focal length of the combination is

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Answer:

Solution:

Equivalent focal length ( $F$ ) of two lenses separated by distance $d$ is given by

$\frac{1}{F} = \frac{1}{f_{1}} + \frac{1}{f_{2}} - \frac{d}{f_{1} f_{2}}$

$= \frac{1}{0.2} + \frac{1}{0.2} - \frac{0.5}{(0.2) (0.2)}$

$= 5 + 5 - 0.5 \times 5 \times 5$

$= 10 - 12.5$

$= - 2.5$

$F = - \frac{1}{2.5} = - 0.4 m$

Stream:NTA_ABHYAS_NEETSubject:PhysicsTopic:Geometrical OpticsSubtopic:Refraction at curved surface/Lens

⏱ 2mℹ️ Source: PYQ_2020

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