KVPY SA Exam 2013 Question Paper

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Question : 45 of 80

Marks: +1, -0

The radii of the first Bohr orbit

H(r_H),He^{+}(r_{\He^{+}})

and

Li^{2+}(r_{\Li^{2+}})

are in the order

$r_{\He^{+}} > r_\H > r_{\Li^{2+}}$
$r_\H < r_{\He^{+}} < r_{\Li^{2+}}$
$r_\H > r_{\He^{+}} > r_{\Li^{2+}}$
$r_{\He^{+}} < r_\H < r_{\Li^{2+}}$

Solution:

r=0.529×n^2/z

r∝1/z

So correct order is

\r_\H > \r_\He^{+} > \r_\Li^{2+}

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