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    Hsslive-xii-4-Concave Lens (Contact Method) - Signed

    Uploaded by

    Aryan Panwar
    This document describes a method to calculate the focal length of a concave lens using a convex lens. It explains that by finding the focal length (f') of the convex lens alone using the u-v method, and then finding the focal length (f) of the combined convex and concave lens system, the focal length (F) of just the concave lens can be determined using the formula F = ff'/(f'-f). An example is then shown to demonstrate how to choose suitable u values for this calculation.

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    Hsslive-xii-4-Concave Lens (Contact Method) - Signed

    Uploaded by

    Aryan Panwar
    12 views2 pages
    This document describes a method to calculate the focal length of a concave lens using a convex lens. It explains that by finding the focal length (f') of the convex lens alone using the u-v method, and then finding the focal length (f) of the combined convex and concave lens system, the focal length (F) of just the concave lens can be determined using the formula F = ff'/(f'-f). An example is then shown to demonstrate how to choose suitable u values for this calculation.

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    Hsslive-xii-4-Concave Lens (Contact method)-signed

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    This document describes a method to calculate the focal length of a concave lens using a convex lens. It explains that by finding the focal length (f') of the convex lens alone using the u-v method, and then finding the focal length (f) of the combined convex and concave lens system, the focal length (F) of just the concave lens can be determined using the formula F = ff'/(f'-f). An example is then shown to demonstrate how to choose suitable u values for this calculation.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    12 views2 pages

    Hsslive-xii-4-Concave Lens (Contact Method) - Signed

    Uploaded by

    Aryan Panwar
    This document describes a method to calculate the focal length of a concave lens using a convex lens. It explains that by finding the focal length (f') of the convex lens alone using the u-v method, and then finding the focal length (f) of the combined convex and concave lens system, the focal length (F) of just the concave lens can be determined using the formula F = ff'/(f'-f). An example is then shown to demonstrate how to choose suitable u values for this calculation.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 2

    39

    Observations and Calculation


    Using Distant object method we can find focal length, based on that chose suitable values
    for u between 1.5*f and 2.5*f
    example if f ’ =10 cm then 1.5x10 = 15cm and 2.5x10 = 25 cm
    then u can be 16,18,20,22,24
    similarly in distant object method, for combined lens if f=18 cm then 1.5x18=27 and
    2.5x18=45 then u can be 28,30,32,34,36 …
    VM
    IC

    Object Mean focal


    AR

    Lens Trail Image distance Focal length


    H

    Distance f=
    𝒖𝒗 length
    used No v in cm
    e:

    u in cm (𝒖+𝒗) f in cm
    ub
    uT
    Yo

    f = ………………… cm f = …………..…..cm
    2
    Convex lens

    3
    4
    5
    6

    1
    Convex lens and
    Concave lens

    2
    3
    4
    5
    6

    𝒇𝒇′
    Focal length of the given concave lens F = = ……………….…. cm
    ( 𝒇′ −𝒇 )
    F = ……………….……m

    HARIKRISHNAN K HSST JR PHY CVM HSS VANDAZHY FOR VIDEO DEMONSTRATION : YOU TUBE : HARI CVM
    40

    CONCAVE LENS
    AIM
    To find focal length of concave lens by contact method
    APPARATUS
    Concave lens, convex lens, screen, illuminated wire gauge.
    THEORY
    If f is the focal length of combination of lens and f ’ is the focal
    length of convex lens , then the focal length of concave lens is
    given by

    𝒇𝒇′
    F=
    ( 𝒇′ −𝒇 )
    PROCRDURE
    VM

    First find the focal length of convex lens ( f ’) using u-v method.
    IC
    AR

    Lens is placed at a distance (u ) from the wire gauze, then by


    H

    adjusting screen clear image is formed. Now image distance (v)


    e:
    ub
    uT

    is measured. This method is repeated for different values of u.


    Yo

    Now the convex and concave lens are placed in contact and
    stick together using insulation tap ( since concave lens can’t
    form real images). Now find the focal length of the combination
    ( f ) using u-v method as explained later. Form f and f ’ calculate
    F of concave lens.

    RESULT
    Focal length of the given concave lens, F = …………..… m

    HARIKRISHNAN K HSST JR PHY CVM HSS VANDAZHY FOR VIDEO DEMONSTRATION : YOU TUBE : HARI CVM

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