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Umme posted an Question
September 17, 2020 • 01:52 am 30 points
  • IIT JAM
  • Physics (PH)

In the x-ray difiraction of a set of crystal planes havingd equal to 0.1 8 nm, frst order reflection is found to be at an angle of 22°. the wavelength of x-ray

In the X-ray difiraction of a set of crystal planes havingd equal to 0.1 8 nm, frst order reflection is found to be at an angle of 22°. The wavelength of X-ray is: (sin 22=0.208): |BHU 2014] (a) 0.0749 nm (b) 0.0374 nm (c) 0.749 nm (d) 0.374 nm

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    Somnath

    Use Bragg's law 2dSin(theta)=n(lamda) Now given d=0.18nm theta=22 degree for first order maximum n=1 lamda = 2dSin(theta) = 2×0.18×Sin22 = 2×0.18×0.208 = 0.07488 nm Answer is Option a.

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    Somnath best-answer

    Use Bragg's law 2dSin(theta)=n(lamda) Now given d=0.18nm theta=22 degree for first order maximum n=1 lamda = 2dSin(theta) = 2×0.18×Sin22 = 2×0.18×0.208 = 0.07488 nm Answer is Option a.

  • Jeevesh magnani Best Answer

    we have used the Bragg's law. please see the attachment for details.

    cropped1651951502.jpg
    eduncle-logo-app

    but what about the fact that sin 22° isn't 0.208 ...it's actually 0.3746

    eduncle-logo-app

    let me put it this way, so it's kind of rule per say, that if some value of some constant is given which doesn't match with the universal value of that constant, we are still supposed to use the value given by the examiner. In some examples in Quantum Mechanics you will see sometimes the examiner asks us to take value of plancks constant as 1, though we know that it's value is 6.626×10-33, we will still use 1

    eduncle-logo-app

    I appreciate that you raised this doubt before exam. During the exam, always follow the question paper, and refrain asking this to even invigilator cause that will hamper your time.

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