A convex lens of focal length 20 cm is placed in contact with a concave lens of focal length 12.5 cm in such a way that they have the same p

Question

A convex lens of focal length 20 cm is placed in contact with a concave lens of focal length 12.5 cm in such a way that they have the same principal axis. Find the power of the combination​

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Anna 2 weeks 2021-09-13T14:31:04+00:00 2 Answers 0 views 0

Answers ( )

    0
    2021-09-13T14:33:00+00:00

    Answer:

    Focal length of concave lens

    • 12.5 cm = – 0.125 m

    Power calculated as

     \\  \sf \: p =  \dfrac{1}{ - 0.125}   \\  \\  \\  \qquad \bullet \sf \:  - 8.3 \: D \\  \\

    Power of convex lens Calculated as

     \\  \sf \: p =  \dfrac{1}{0 - 20}  \\  \\  \\ \qquad \bullet \sf \:  - 5 \: D \\  \\

    Power of combination

     \\  \sf \: 5 - 8.3 \\  \\  \\  \implies \sf \: 3.3 \: D \\  \\

    Focal length of concave lens Calculated as

     \\  \sf \: f =  - 10 \: cm =  \frac{ - 10}{100}  \\  \\  \\  \qquad \bullet \sf \: 0.1 \: m. \\  \\

    Power

     \\  \sf \: p =  \frac{1}{ - 0.1}  \\  \\  \\  \qquad \sf \bullet \: 10 \: D \\  \\

    Focal length of convex lens

    • 20 cm = 0.2 m.

     \\ \sf p =  \dfrac{1}{f}  \\  \\  \\  \sf \: p =  \dfrac{1}{0.20}  \\  \\  \\  \implies \sf \: 5 \: D \\  \\

    Power of combination

     \\  \sf \: 5 - 10 \\  \\  \\  \implies \sf \blue{ - 5 \: D} \\  \\

    0
    2021-09-13T14:33:03+00:00

    Answer:

    Focal length of concave lens –

    12.5 cm = – 0.125 m

    Power calculated as –

    \begin{gathered} \\ \sf \: p = \dfrac{1}{ – 0.125} \\ \\ \\ \qquad \bullet \sf \: – 8.3 \: D \\ \\ \end{gathered}

    p=

    −0.125

    1

    ∙−8.3D

    Power of convex lens Calculated as –

    \begin{gathered} \\ \sf \: p = \dfrac{1}{0 – 20} \\ \\ \\ \qquad \bullet \sf \: – 5 \: D \\ \\ \end{gathered}

    p=

    0−20

    1

    ∙−5D

    Power of combination –

    \begin{gathered} \\ \sf \: 5 – 8.3 \\ \\ \\ \implies \sf \: 3.3 \: D \\ \\ \end{gathered}

    5−8.3

    ⟹3.3D

    Focal length of concave lens Calculated as –

    \begin{gathered} \\ \sf \: f = – 10 \: cm = \frac{ – 10}{100} \\ \\ \\ \qquad \bullet \sf \: 0.1 \: m. \\ \\ \end{gathered}

    f=−10cm=

    100

    −10

    ∙0.1m.

    Power –

    \begin{gathered} \\ \sf \: p = \frac{1}{ – 0.1} \\ \\ \\ \qquad \sf \bullet \: 10 \: D \\ \\ \end{gathered}

    p=

    −0.1

    1

    ∙10D

    Focal length of convex lens –

    20 cm = 0.2 m.

    \begin{gathered} \\ \sf p = \dfrac{1}{f} \\ \\ \\ \sf \: p = \dfrac{1}{0.20} \\ \\ \\ \implies \sf \: 5 \: D \\ \\ \end{gathered}

    p=

    f

    1

    p=

    0.20

    1

    ⟹5D

    Power of combination –

    \begin{gathered} \\ \sf \: 5 – 10 \\ \\ \\ \implies \sf \blue{ – 5 \: D} \\ \\ \end{gathered}

    5−10

    ⟹−5D

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