If the velocity of the electron is 1.6 × 10⁶ ${\mathrm{ms}}^{-1}$. The de Broglie wavelength associated with this electron is:  

$1.$ $590$ $\mathrm{pm}$
$2.$ $455$ $\mathrm{pm}$
$3.$ $512$ $\mathrm{pm}$
$4.$ $401$ $\mathrm{pm}$

The ratio of the wavelengths of the last lines of the Balmer to Lyman series is

A photon detector receives a total energy of \(3.15 \times 10^{-18}\) J from radiation with a wavelength of 600 nm. How many photons are received by the detector?

$1.$ ${10}^2$
$2.$ $10$
$3.$ $50$
$4.$ $20$

The wave number for the longest wavelength transition in the Balmer series of atomic hydrogen would be :

\(1 .   1 . 52   \times   10^{6}   m^{- 1}\)
\(2 .   3 . 14   \times   10^{6}   \left(cm\right)^{- 1}\)
\(3 .   15 . 2   \times   10^{6}   m^{- 1}\)
\(4 .   1 . 52   \times   10^{6}   \left(cm\right)^{- 1}\)

The wavelength of light emitted when the electron in a H atom undergoes the transition from an energy level with n = 4 to an energy level with n = 2, is :

1. 586 mm

2. 486 nm

3. 523 nm

4. 416 pm

A 25-watt bulb emits monochromatic yellow light with a wave length of 0.57µm. The rate of emission of quanta per second would be :

1. 7.17 × 10^–19 s^–1

2. 4.13 × 10¹⁶ s^–1

3 . 7.17 × 10¹⁹ s^–1

4 . 1.26 × 10²⁰ s^–1
${\mathrm{}}^{}$

If the electronic structure of oxygen atom is written as $1{\mathrm{s}}^2,<mspace\; width="1em"></mspace>2{\mathrm{s}}^2$  it would violate:

1. Hund's rule.

2. Paulis exclusion principle.

3. Both Hund's and Pauli's principles.

4. None of the above.