IIT JAM
Himanshu Pandey Asked a Question
May 28, 2020 12:54 pmpts 30 pts
  • IIT JAM
  • Physics (PH)

Optics two lenses of focal length 10cm and 20cm......

Here I am asking two different question Q.1 From pic 1 it's solution and most importantly what is achromatic double???? provide me it's all formula/condition. Q.2 From pic 2&3 here it's obtaining total power of the attached figure but why there is a minus in combined power (highlighted) how sign convention is used there ???
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  • Himanshu Pandey
    but i got it thanks
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  • Himanshu Pandey
    Abhishek sir it's answer is given 13.6cm not 15
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  • Himanshu Pandey
    yes rubii mam page 1& 3 are different question
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  • Chandra dhawan
    achromatic lens-doublet is formed by placing in contact a convex lens of focal length f1 and a concave lens of focal length f3....... I hope u understood it
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    Chandra dhawan
    f3* ...replace by f2.
  • Abhishek singh thankyou
    For your first doubt. Achromatic double means, combination of two lenses such that the chromatic Aberration is removed. and it's condition is attached alongwith. Do read this comme...
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    Abhishek singh
    this method has already been discussed in one of your previous doubts. They have changed the language of question. But they have asked the same concept.
  • Abhishek singh Best Answer
    Solution for second part of your question. Do ask doubts if any. actually powers are always add when lenses are in contact. but here the power itself is negative for Plano concave ...
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    • cropped8956732998023180629.jpg
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    Abhishek singh
    do remember these methods of solving questions.
  • Vaishnavi rajora thankyou
    dear see attached.
    • cropped4113135293535691044.jpg
    • cropped3523766497686572791.jpg
    • cropped8518943428472364256.jpg
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    Vaishnavi rajora
    see the solution for the first one.
  • Ruby negi
    ohmega 1 and omega 2 in last page is dispersive power of lens 1 and lens 2.
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  • Ruby negi
    page 1 and page 3 are different question, right?
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  • Vaishnavi rajora
    dear in second question..... as we know total power should be sum of power of both lenses but it's negative due to direction of their focus distance. and the factor of two must be ...
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