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

The electronic transition in the hydrogen atom that emits maximum energy is:

1. 2 $\to$ 1

2. 1 $\to$ 4

3. 4 $\to$ 3

4. 3 $\to$ 2