The de-Broglie's wavelength of electron present in first Bohr orbit of 'H' atom is :
0.529 $\mathop {\rm A}\limits^ \circ $
2$\pi $ $ \times $ 0.529 $\mathop {\rm A}\limits^ \circ $
${{0.529} \over {2\pi }}$ $\mathop {\rm A}\limits^ \circ $
4 $ \times $ 0.529 $\mathop {\rm A}\limits^ \circ $
