Which of the following sets of quantum numbers is not possible ?

• n = 4 , l =1 , m = 0 , s = $+ \frac{1}{2}$

• n = 4 , l = 3 , m = - 3 , s = $- \frac{1}{2}$

• n = 4 , l = 1 , m = + 2 , s = $- \frac{1}{2}$

• n = 4 , l = 0 , m = 0 , s = $- \frac{1}{2}$

What is the frequency of a X-ray photon whose momentum is 1.1 x 10^-23 kg-ms^-2 ?

• 5 x 10¹⁶ Hz

• 0.5 x 10²⁷ Hz

• 0.5 x 10¹⁸ Hz

• 5 x 10¹⁸ Hz

The magnitude of orbital angular momentum of an electron of azimuthal quantum number 2 is :

• $\frac{2\mathrm{h}}{2\mathrm{\pi }}$

• $\frac{\sqrt{6}\mathrm{h}}{2\mathrm{\pi }}$

• $\frac{\sqrt{2}\mathrm{h}}{2\mathrm{\pi }}$

• $\frac{6\mathrm{h}}{2\mathrm{\pi }}$

For an electron , if the uncertainty in velocity is $∆$v , the uncertainty in its position ($∆$x)  is given by :

• $\frac{\mathrm{hm}}{4\mathrm{\pi }∆\mathrm{\nu }}$

• $\frac{4\mathrm{\pi }}{\mathrm{hm}∆\mathrm{\nu }}$

• $\frac{\mathrm{h}}{4\mathrm{\pi m}∆\mathrm{v}}$

• $\frac{4\mathrm{\pi m}}{\mathrm{h}∆\mathrm{\nu }}$

A metal surface is exposed to solar radiations :

• the emitted electrons have energy less than a maximum value of energy depending upon frequency of incident radiations

• the emitted electrons have energy less than maximum value of energy depending upon intensity of incident radiations

• the emitted electrons have zero energy

• the emitted electrons have energy equal to energy of photons of incident light

Which of the following transitions have minimum wavelengths ?

• n₄ $\to$ n₁

• n₂ $\to$ n₁

• n₄ $\to$ n₂

• n₃ $\to$ n₁

Orbital is :

• circular path around the nucleus in which the electrons revolves

• space around the nucleus where the probability of finding the electron is maximum

• amplitude of electron wave

• none of the above

378.

Which of the following sequence is correct as per Aufbau principle ?

• 3s < 3d < 4s < 4p

• ls < 2p < 4s < 3d

• 2s < 5s < 4p < 5d

• 2s < 5s < 4p < 5f

A radioactive nucleus will not emit :

• alpha and beta rays simultaneously

• beta and gamma rays simultaneously

• gamma and alpha rays

• gamma rays only

X-rays are emitted during

• $\mathrm{\alpha }$, n reaction

• K-capture

• n, $\mathrm{\alpha }$-reaction

• $\mathrm{\beta }$- emission