Atoms

J.J. Thomson's cathode ray tube experiment demonstrated- that

• cathode rays are streams of negatively charged ions

• all the mass of an atom is essentially in the nucleus

• the e/m of electrons is much greater than the e/m of protons.

• the e/m ratio of the cathode ray particles changes when a different gas is placed in the discharged tube

Wavelength of light emitted from second orbit to first orbit in a hydrogen atom is

• 6563 A^o

• 4102 A^o

• 4861 A^o

• 1215 A^o

If λ₁ and λ₂ are the wavelengths of the first members of the Lyman and Paschen series respectively, then λ₁ : λ₂ is

• 1:3

• 1: 30

• 7: 50

• 7: 108

Minimum excitation potential of Bohr's first orbit in hydrogen atom is

• 3.6 V

• 10.2 V

• 13.6 V

• 3.4 V

Ionisation potential of hydrogen atom is 13.6 eV. Hydrogen atom on the ground state rarely excited by monochromatic radiation of photon 12.1 eV. The special line emitted by a hydrogen atom according to Bohr's theory will be

• one

• two

• three

• four

According to Bohr's model of hydrogen atom, relation between principal quantum number n and radius of stable orbit is

• r ∝ $\frac{1}{\mathrm{n}}$

• r ∝ n

• r ∝ $\frac{1}{{\mathrm{n}}^2}$

• r ∝ n²

The de-Broglie wavelength of electron falling on the target in an X-ray tube is),. The cut-off wavelength of the emitted X-ray is

• ${\mathrm{\lambda }}_0 = \frac{{\left( \mathrm{m} \mathrm{c} \mathrm{\lambda } \right)}^2}{\mathrm{h}}$

• ${\mathrm{\lambda }}_0 = \frac{{\mathrm{m}}^2 \mathrm{c\lambda }}{{\mathrm{h}}^2}$

• ${\mathrm{\lambda }}_0 = \frac{2 \mathrm{mc} {\mathrm{\lambda }}^2}{\mathrm{h}}$

• ${\mathrm{\lambda }}_0 = \frac{\mathrm{m} \mathrm{c} {\mathrm{\lambda }}^2}{{\mathrm{h}}^2}$

If a proton and anti-proton come close to each other and annihilate, how much energy will be released?

• 1.5 × 10^-10 J

• 3 × 10^-10 J

• 4.5 × 10^-10 J

• 2 ×  10^-10 J

A body at rest slides down a 30° inclined plane. The time taken by it to slide down is twice the time it takes when it slides down the same distance in the absence of friction. The coefficient of friction between the body and the inclined plane is

• 0.43

• 0.37

• 0.64

• 0.75

An energy of 68.0 eV is required to excite a hydrogen-like atom in its second Bohr energy level to third energy level the charge of nucleus is Ze. The wavelength of a radiation required to eject the electron from first orbit to infinity is

• 2.2 nm

• 2.85 nm

• 3.2 nm

• 2.5 nm