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

Helium atom can be excited to 1s¹, 2p¹ configuration by light of 58.44 nm. The lowest excited state with configuration 1s¹, 2s¹ lies 4857 cm^-1 (1/$\mathrm{\lambda }$) below the 1s¹, 2p¹ state. What would be the average He - H bond energy so that HeH₂ could form, non-endothermically from the lowest excited singlet state of helium? Neglect any difference between $∆$G and $∆$H and take $∆$H as 218 kJ mol^-1

1. 1614 kJ mol^-1

2. 1212 kJ mol^-1

3. 912 kJ mol^-1

4. 1511 kJ mol^-1

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 frequency of the X-rays produced using an element as anti-cathode is found to be 2500 sec^-1, the atomic number of used element is (a, b= 1)

1. 51

2. 49

3. 56

4. 72

What is the energy required per mole to excite an electron from the third to fifth Bohr orbit in hydrogen ?

1. 6.336 x 10⁶J

2. 7.122 x 10⁴J

3. 0.343 x 10⁶J

4. 9.343 x 10⁴J

The energy of electron in first Bohr's orbit of H-atom is -13.6 eV. What will be its potential energy in n = 4.

1. –13.6 eV

2. - 3.4 eV

3. -0.85 eV

4. -1.70 eV

Sodium atoms can be ionised by supplying an energy of 118 kcal mol^-1. Using this data, calculate the lowest possible frequency of light that can ionise a sodium atom.

(h = 6.624 x 10^-27 erg.sec, c= 3 x 10¹⁰ cm sec^-1).

1. 1.24 x 10¹⁵ sec^-1

2. 0.24 x 10¹⁵ sec^-1 

3. 12.4 x 10¹² sec^-1

4. 2.31 x 10¹⁸ sec^-1

A glow worm of mass 5.0 g emits red light (650 nm) with a power of 0.1 W. entirely in the backward direction. What velocity would it accelerate to after 10 years, if released in free space (and assumed to be alive)?

1. 9.14 ms^-1 

2. 28.08 ms^-1

3. 11.05 ms^-1

4. 21.04 ms^-1

Which of the following postulates does not belong to Bohr's model of the atom?

1. Angular momentum is an integral multiple of h/2$\mathrm{\pi }$

2. The electron stationed in the orbit is stable

3. The path of an electron is circular

4. The change in the energy levels of electron is continuous