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

The ratio of longest wavelengths corresponding to the Lyman and Blamer series in hydrogen spectrum is :

Monochromatic radiation emitted when electron on hydrogen atom jumps from first excited to the ground state irradiates a photosensitive material. The stopping potential is measured to be 3.57 V. The threshold frequency of the material is

If the nucleus ${}_{13}{}^{27}\mathrm{Al}$ has a nuclear radius of about 3.6 fermi, then ${}_{52}{}^{125}\mathrm{Te}$ would have its radius approximately as:

In a discharge tube ionization of enclosed gas is produced due to collisions between:

The radius of Germanium (Ge) nuclide is measured to be twice the radius of ${}_4{}^9\mathrm{Be}$. The number of nucleons in Ge are:

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

$\alpha$-particle consists of:

An electron and a proton are separated by a large distance. The electron starts approaching the proton with energy 2eV. The proton captures the electron and forms a hydrogen atom in first excited state. The resulting photon is incident on a photosensitive metal of threshold wavelength 4600Å. The maximum K.E. of the emitted photoelectron is (Take hc = 12420 eV Å)

The radius of the first permitted Bohr orbit for the electron in a hydrogen atom equals $0.5 \stackrel{o}{A}$ and its ground state energy equals -13.6 eV. If the electron in the hydrogen atom is replaced by muon $\left({\mu }^{-}\right)$ [ charge same as electron and mass 207$m_e$], the first Bohr radius and ground state energy will be-   ($m_e$ represents mass of electron)

An electron in Bohr's hydrogen atom has angular momentum $\frac{2h}{\mathrm{\pi }}$. The energy of the electron is 

If the energy of the electron in an H-atom in the ground state is taken to be -13.6 eV, then the kinetic energy of the electron in the first excited state will be:

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

Which one of the following is not true:

What is the shortest wavelength present in the Paschen series of spectral lines?

A difference of 2.3 eV separates two energy levels in an atom. What is the frequency of radiation emitted when the atom makes a transition from the upper level to the lower level?

$$\begin{gathered} \left(1\right) 6.6\times {10}^{14} Hz. \\ \left(2\right) 5.6\times {10}^{14} Hz. \\ \left(3\right) 9.3\times {10}^{14} Hz. \\ \left(4\right) 7.9\times {10}^{14} Hz. \end{gathered}$$

The ground state energy of the hydrogen atom is –13.6 eV. What is the potential energy of the electron in this state?

The radius of the innermost electron orbit of a hydrogen atom is $5.3\times {10}^{-11} m.$ What is the radius of the n = 2 orbit?

$$\begin{gathered} \left(1\right) 1.67 \stackrel{0}{A} \\ \left(2\right) 4.77 \stackrel{0}{A} \\ \left(3\right) 2.12 \stackrel{0}{A} \\ \left(4\right) 3.11 \stackrel{0}{A} \end{gathered}$$

A hydrogen atom initially in the ground level absorbs a photon, which excites it to the n = 4 level. The wavelength of photon is:

The speed of the electron in a hydrogen atom in the n = 1 level is:

$$\begin{gathered} \left(1\right) 1.1\times {10}^6 m/s \\ \left(2\right) 2.18\times {10}^6 m/s \\ \left(3\right) 1.08\times {10}^6 m/s \\ \left(4\right) 3.07\times {10}^6 m/s \end{gathered}$$

In accordance with Bohr’s model, what is the quantum number that characterizes the earth’s revolution around the sun in an orbit of radius $1.5\times {10}^{11} m$  with orbital speed $3\times {10}^4 m/s$? (Mass of earth = $6.0\times {10}^{24} kg.$)

$$\begin{gathered} \left(1\right) 1.8\times {10}^{76} \\ \left(2\right) 2.3\times {10}^{74} \\ \left(3\right) 1.3\times {10}^{76} \\ \left(4\right) 2.6\times {10}^{74} \end{gathered}$$

The total energy of an electron in the first excited state of the hydrogen atom is about -3.4 eV. What is the kinetic energy of the electron in this state?

The total energy of an electron in the first excited state of the hydrogen atom is about -3.4 eV. What is the potential energy of the electron in this state?

The ground state energy of a muonic hydrogen atom is:

(Mass of a negatively charged muon, $m_{\mu }=207 m_e$)

The minimum wavelength of X-rays produced by 30 kV electrons is:

An X-ray tube produces a continuous spectrum of radiation with its short wavelength end at 0.45 Å. What is the maximum energy of a photon in the radiation?

$$\begin{gathered} \left(1\right) 27.6 keV \\ \left(2\right) 25.5 keV \\ \left(3\right) 23.4 keV \\ \left(4\right) 25.1 keV \end{gathered}$$

Taking the Bohr radius as ${\mathrm{a}}_0=53 \mathrm{pm}$, the radius of Li⁺⁺ ion in its ground state, on the basis of Bohr's model, will be about:

The binding energy of a H-atom, considering an electron moving around a fixed nucleus (proton), is,

$\mathrm{B}=-\frac{{\mathrm{me}}^4}{8{\mathrm{n}}^2{\mathrm{\epsilon }}_0^2{\mathrm{h}}^2}$ (m = electron mass)
If one decides to work in a frame of reference where the electron is at rest, the proton would be moving around it. By similar arguments, the binding energy would be,

$\mathrm{B}=-\frac{{\mathrm{Me}}^4}{8{\mathrm{n}}^2{\mathrm{\epsilon }}_0^2{\mathrm{h}}^2}$ (M = proton mass)
This last expression is not correct, because,