When accelerated electrons are direct against an anticathode in an X-ray tube, the radiation obtained has a continuous spectrum with a wavelength minimum,

${\lambda }_{min} =\frac{ (1.24 x {10}^{-6})}{V}$) m, where V is the voltage used for accelerating the electrons.

Calculate $\lambda$_min for V= 5 x 10⁴ volts.

1. 1.25 Å

2. 0.75 Å

3. 0.25 Å

4. 1.00 Å

The wavelengths of two photons are 2000 Å and 4000 Å respectively. What is the ratio of their energies?

1. 1/4

2. 4

3. 1/2

4. 2

The number of electrons in one molecule of CO₂ are - 

1. 22

2. 44

3. 66

4. 88

The ion that is isoelectronic with CO is-

1. CN^-

2. O₂⁺

3. O₂^-

4. N₂⁺

If uncertainity in position and momentum are equal, the uncertainty in velocity is:

1. $\sqrt{h/2\mathrm{\pi }}$

2. $\frac{1}{2m}\sqrt{h/\mathrm{\pi }}$

3. $\sqrt{h/\mathrm{\pi }}$

4. None

When the atoms of gold sheet are bombarded with a beam of $\alpha$ -particles, only a few a-particles get deflected where as most of them go straight undeflected. This is because:

The number of electrons in the valence shell of calcium is 

1. 6

2. 8

3. 2

4. 4

The brackett series of spectral lines arise when an electron in an excited hydrogen atom jumps from an energy level

1. n=5 to n=1

2. n=5 to n=3

3. n=5 to n=4

4. n=5 to n=2

The ratio of the wavelengths of the last lines of the Balmer and Lyman series is:

1. 4:1

2. 27:5

3. 3:1

4. 9:4

The splitting of spectral lines in a magnetic field, arising out of the orbital motion of
electrons only, and the further splitting due to spin motion are respectively called:

1. Zeeman and Stark effects

2. Zeeman and anomalous Zeeman effects

3. Stark and Zeeman effects

4. Zeeman and Kerr effects