Atoms

Let T1 and T2 be the energy of an electron in the first and second excited states of hydrogen atoms, respectively. According to the Bohr's model of an atom, the ratio T1 : T2 is

1. 1 : 4
2. 4 : 1
3. 4 : 9
4. 9 : 4

Let R1 be the radius of the second stationary orbit and R2 be the radius of the fourth stationary orbit of an electron in Bohr's model. The ratio R1R2 is :

1. 4
2. 0.25
3. 0.5
4. 2

For which one of the following, Bohr model is not valid?

1. Singly ionised helium atom (He+)
2. Deuteron atom
3. Singly ionised neon atom (Ne+)
4. Hydrogen atom

-particle consists of :

1. 2 electrons, 2 protons and 2 neutrons
2. 2 electrons and 4 protons only
3. 2 protons only
4. 2 protons and 2 neutrons only

The total energy of an electron in an atom in an orbit is -3.4 eV. Its kinetic and potential energies are, respectively.

1. 3.4 eV, -6.8 eV
2. 3.4 eV, 3.4 eV
3. -3.4 eV, -3.4 eV
4. -3.4 eV, -6.8 eV

The ratio of kinetic energy to the total energy of an electron in a Bohr orbit of the hydrogen atom, is

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

The ratio of wavelengths of the last line of Balmer series and the last line of Lyman series is

1. 1
2. 4
3. 0.5
4. 2

Given the value of Rydberg constant is 107 m-1, the wave number of the last line of the Balmer series in hydrogen spectrum will be

1. 0.25 107 m-1
2. 2.5 107 m-1
3. 0.025 104 m-1
4. 0.5 107 m-1

When an -particle of mass m moving with velocity v bombards on a heavy nucleus of charge Ze, its distance of closest approach from the nucleus depends on m as

1. 1m2
2. m
3. 1m
4. 1 m

Electrons of mass m with de-Broglie wavelength fall on the target in an X-ray tube. The cutoff wavelength ( 0) of the emitted X-ray is

1. 0 = 2mc 2h
2. 0 = 2hmc
3. 0 = 2m2c2 3h2
4. 0 =