The total number of neutrons in dipositive zinc ions with mass number 70 is -

1. 34

2. 40

3. 36

4. 38

With a certain exciting radiation of a particular frequency, to which hydrogen atoms are exposed, the maximum number of spectral lines obtainable in the emission is 15. The uppermost energy level to which the electron is excited is 

1. 4

2. 5

3. 6

4. 7

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