If $\lambda_0$ and $\lambda$ are respectively the threshold wavelength and wavelength of incident light the velocity of photo electrons ejected from the metal surface is

The energy of third orbit of $\mathrm{Li}^{2+}$ ion (in J ) is

The number of $d$ electrons in Fe is equal to which of the following?

(i) Total number of ' $s$ ' electrons of Mg .

(ii) Total number of ' $p$ ' electrons of Cl .

(iii) Total number of ' $p$ ' electrons of Ne .

The correct option is

If uncertainty in position and momentum of an electron are equal, then uncertainty in its velocity is