Atoms

Ionization potential of hydrogen atom is 13.6 eV. Hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy 12.1 eV. According to Bohr's theory, the spectral lines emitted by hydrogen will be

• two 

• three

• four

• four

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

• 2

• 1

• 4

• 4

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

• 1:1

• 1:-1

• 1:-2

• 2:-1

An electron of mass m with an initial velocity $\overrightarrow{V} = V_o\hat{i} (V_o>0)$ enters an electric field $\overrightarrow{E} = - E_o \hat{i}$ (E₀ constant >0) at t = 0. if λ₀ is its de-Broglie wavelength initially, then its de-Broglie wavelength at time t is

• $\frac{{\lambda }_0}{\left(1+{\displaystyle \frac{e{E}_0}{m{V}_0}}t\right)}$

• ${\lambda }_o\left(1 + \frac{e{E}_0}{m{V}_0}t\right)$

• ${\lambda }_0$

• ${\lambda }_{0}t$

The potential of an atom is given by V = V₀loge(r/r₀) where r₀ is a constant and r is the radius of the orbit. Assuming Bohr's model to be applicable, which variation or r_n with n is possible (n being a principal quantum number)?

• ${\mathrm{r}}_{\mathrm{n}} \propto \mathrm{n}$

• ${\mathrm{r}}_{\mathrm{n}} \propto \frac{1}{\mathrm{n}}$

• ${\mathrm{r}}_{\mathrm{n}} \propto {\mathrm{n}}^2$

• ${\mathrm{r}}_{\mathrm{n}} \propto \frac{1}{{\mathrm{n}}^2}$

The electric potential at the surface of an atomic nucleus (Z = 50) of radius 9.0$\times {10}^{-15}$m is

• 8$\times {10}^6 \mathrm{V}$

• 80V

• $9\times {10}^{5 }\mathrm{V}$

• 9V

The radius of electron second stationary orbit in Bohr's atom is R. The radius of third orbit will be

• 2.25R

• 3R

• R/3

• 9R

The kinetic energy of an electron is 5eV. Calculate the de-Broglie wavelength associated with it (h=6.6×10^-34 Js, m_e =9.1×10^-31 kg)

• 5.47A^o

• 10.9A^o

• 2.7A^o

• None of these

Radius of first Bohr orbit is r. What is the radius of 2nd Bohr orbit ?

• 8 r

• 2 r

• 4 r

• $2\sqrt{2} \mathrm{r}$

Copper has face-centred cubic ( FCC ) lattice with interatomic spacing equal to 2.54 A. The value of lattice constant for this lattice is

• 1.27 A^o

• 5.08 A^o

• 2.54 A^o

• 3.59 A^o