A gas of H-atoms in excited state absorbs a photon of some energy and jump in higher energy state . Then it returns to ground state after emitting six different wavelengths in emission spectrum. The energy of emitted photon is equal, less or greater than the energy of absorbed photon then and will be
1. =5, =3
2. =5, =2
3. =4, =3
4. =4, =2
An particle with a kinetic energy of 2.1 eV makes a head on collision with a hydrogen atom moving towards it with a kinetic energy of 8.4 eV. The collision
1. must be perfectly elastic
2. may be perfectly inelastic
3. may be inelastic
4. must be perfectly inelastic
- particles of energy 400 KeV are bombarded on nucleus of . In scatterng particles, its minimum distance from nucleus will be
1. 0.59 nm
2. 0.59
3. 5.9 pm
4. 0.59 pm
If in Rutherford's experiment, the number of particles scattered at 90 angle are 28 per min, then the number of scattered particles at an angle 60 and 120 will be
1. 112/min, 12.5/min
2. 100/min, 200 /min
3. 50/min. 12.5 /min
4. 117/min, 25/min
The number of revolutions per second made by an electron in the first Bohr orbit of hydrogen atom is of the order of :
1.
2.
3.
4.
Hydrogen (H), Deuterium (D), singly ionized helium and doubly ionized lithium () all have one electron around the nucleus. Consider n = 2 to n = 1 transition. The wavelengths of emitted radiations are respectively. Then approximately
1.
2.
3.
4.
An energy of 24.6 eV is required to remove one of the electrons from a neutral helium atom. The energy (in eV) required to remove both the electrons from a neutral helium atom is
1. 79.0
2. 51.8
3. 49.2
4. 38.2
In hydrogen atom, electron makes transition from n = 4 to n = 1 level. Recoil momentum of the H atom will be
1.
2.
3.
4.
The ratio of the speed of the electrons in the ground state of hydrogen to the speed of light in vacuum is
1. 1/2
2. 2/137
3. 1/137
4. 1/237
In Milikan's oil drop experiment an oil drop of radius r and charge Q is held in equilibrium between the plates of a charged parallel plate capacitor when the potential difference is V. To keep a drop of radius 2r and with a charge 2Q in equilibrium between the plates the potential difference V required is :
1. V
2. 2V
3. 4V
4. 8V
In the spectrum of hydrogen atom, the ratio of the longest wavelength in Lyman series to the longest wavelength in the Balmer series is
1. 5/27
2. 1/93
3. 4/9
4. 3/2
Figure shows the energy levels P,Q,R,S and G of an atom where G is the ground state. A red line in the emission spectrum of the atom can be obtained by an energy level change from Q to S. A blue line can be obtained by following energy level change
1. P to Q
2. Q to R
3. R to S
4. R to G
Orbital acceleration of electron is
1.
2.
3.
4.