Atoms

In an alpha particle scattering experiment distance of closest approach for the particle is 4.5 10-14 m. If target nucleus has atomic number 80 , then maximum velocity of -particle is 105 m/s approximately. ( 14 0 = 9 109 SI unit, mass of particle = 6.72 10-27 kg)

The ratio of the shortest wavelength of Balmer series to the shortest wavelength of Lyman series for hydrogen atom is :

1. 1 : 2
2. 1 : 4
3. 2 : 1
4. 4 : 1

Radius of a certain orbit of hydrogen atom is 8.48 Å. If energy of electron in this orbit is E/x, then x = (Given a0 = 0.529 Å, E = energy of electron in ground state).

The longest wavelength associated with Paschen series is : (Given RH = 1.097 107 SI unit)

1. 2.973 10-6 m
2. 1.876 10-6 m
3. 1.094 10-6 m
4. 3.646 10-6 m

In Franck-Hertz experiment, the first dip in the current-voltage graph for hydrogen is observed at 10.2 V. The wavelength of light emitted by hydrogen atom when excited to the first excitation level is nm. (Given hc = 1245 eV nm, e = 1.6 10-19 C).

An electron rotates in a circle around a nucleus having positive charge Ze. Correct relation between total energy (E) of electron to its potential energy (U) is :

1. 2E = 3U
2. E = U
3. 2E = U
4. E = 2U

The angular momentum of an electron in a hydrogen atom is proportional to : (Where r is the radius of orbit of electron)

1. 1r
2. 1 r
3. r
4. r

The shortest wavelength of the spectral lines in the Lyman series of hydrogen spectrum is 915 Å. The longest wavelength of spectral lines in the Balmer series will be Å.

A hydrogen atom changes its state from n=3 to n=2. Due to recoil, the percentage change in the wavelength of emitted light is approximately 1 10-n. The value of n is . [Given Rhc=13.6 eV, hc=1242 eV nm, h=6.6 10-34 J s, mass of the hydrogen atom =1.6 10-27 kg]

According to Bohr's theory, the moment of momentum of an electron revolving in 4th orbit of hydrogen atom is:

1. 2 h
2. h2
3. h
4. 8 h