NEET AIPMT SOLVED PAPER SCREENING 2008

  • question_answer
    If ?a? stands for the edge length of the cubic systems : simple cubic, body centred cubic and face centred cubic, then the ratio of radii of the spheres in these systems will be respectively,

    A) \[\frac{1}{2}a;\frac{\sqrt{3}}{4}a:\frac{1}{2\sqrt{2}}a\]  

    B) \[\frac{1}{2}a;\sqrt{3}a:\frac{1}{\sqrt{2}}a\]       

    C) \[\frac{1}{2}a:\frac{\sqrt{3}}{2}a:\frac{\sqrt{2}}{2}a\]    

    D) \[1a:\sqrt{3}a:\sqrt{2}a\]

    Correct Answer: A

    Solution :

    For simple cubic, a = 2r \[\therefore \]\[r=\frac{a}{2}\]For body centred cubic, \[a=\frac{4r}{\sqrt{3}}\] \[r=\frac{\sqrt{3}a}{4}\] For face centred cubic, \[a=2\sqrt{2}r\] \[r=\frac{a}{2\sqrt{2}}\] Hence, the ratio of radii in simple cubic, body centred cubic and face centred cubic is \[\frac{a}{2}:\frac{\sqrt{3}a}{4}:\frac{a}{2\sqrt{2}}\]


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