A X-ray tube operates at an accelerating potential of 20 kV. Which of the following wavelength will be absent in the continuous spectrum of X-rays?

The longest and shortest wavelength of the Lyman series are (respectively)

The frequency Of radiation emitted during the transition of an electron from a second excited state to a first excited state in H-atom is ${\mathrm{f}}_0.$ The frequency of the same transition emitted by a singly ionized He ion is

When the electron of a hydrogen-like atom jumps from a higher energy level to a lower energy level, then,

The energy of a hydrogen atom in its ground state is —13.6 eV. The energy of the level corresponding to the quantum number n = 2 (first excited state) in the hydrogen atom is:

Magnetic moment due to the motion of the electron in ${\mathrm{n}}^{\mathrm{th}}$  energy state of a hydrogen atom is proportional to

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

Given the value of Rydberg constant is ${10}^7 m^{-1}$, the wave number of the last line of the Balmer series in hydrogen spectrum will be:

(a) $0.5\times {10}^7{m}^{-1}$        (b) $0.25\times {10}^7{m}^{-1}$

(c) $2.5\times {10}^7{m}^{-1}$        (d) $0.025\times {10}^4{m}^{-1}$

Consider 3rd orbit of He+ (Helium ion), using the non-relativistic approach, the speed of the electron in this orbit will be:
(Given: Constant K=9x10⁹ Z=2 and Planck's constant, h=6.6x10^-34 J-s)

Hydrogen atom in ground state is excited by a monochromatic radiation of λ=975Å. The number of spectral lines in the resulting spectrum emitted will be:

Electron in hydrogen atom first jumps from third exicted state to second exicted state and then from second exicted to the first excited state. The ratio of the wavelengths ${\lambda }_1:{\lambda }_2$ emitted in the two cases is

An electron of a stationary hydrogen atom passes from the fifth energy level to the ground level. The velocity that the atom acquired as a result of photon emission will be

(m is the mass of the hydrogen atom, R Rydberg constant and h Planck's constant)

The transition from the state n=3 to n=1

a hydrogen like atom results in ultraviolet

radiation. Infrared radiation will be obtained

in the transition from

The wavelength of the first line of Lyman series for hydrogen atom is equal to that of the second line of Balmer series for a hydrogen-like ion. The atomic number Z of hydrogen-like ion is: 

An electron in the hydrogen atom jumps from nth excited state to the ground state. The wavelength so emitted illuminates a photosensitive material having work function 2.75 eV. If the stopping potential of the photo-electron is 10V, the value of n is 

The energy of a hydrogen atom in the ground state is -13.6 eV. The energy of a ${\mathrm{He}}^{+}$ ion in the first excited state will be:

An alpha nucleus of energy $\frac{1}{2}m{v}^2$ bombards a heavy nuclear target of charge Ze. Then the distance of closest approach for the alpha nucleus will be proportional to

The electron in the hydrogen atom jumps from excited state $\left(n=3\right)$ to its ground state $\left(n=1\right)$ and the photons thus emitted irradiate a photosensitive material. If the work function of the material is $5.1 \mathrm{eV},$ the stopping potential is estimated to be (the energy of the electron in the nth state ${\mathrm{E}}_{\mathrm{n}}=-\frac{13.6}{{\mathrm{n}}^2}\mathrm{eV}$)

In a Rutherford scattering experiment when a projectile of charge $Z_1$ and mass $M_1$ approaches a target nucleus of charge $Z_2$ and mass $M_2,$ the distance of closest approach is $r_0$. The energy of the projectile is 

The ionization energy of the electron in the hydrogen atom in its ground state is 13.6 eV. The atoms are excited to higher energy levels to emit radiations of 6 wavelengths. Maximum wavelength of emitted radiation corresponds to the transition between

The ground state energy of hydrogen atom is -13.6 eV. When its electron is in the first excited state, its excitation energy is:

In the phenomenon of electric discharge through gases at low pressure, the coloured glow in the tube appears as a result of:

The ratio of momenta of an electron and an $\mathrm{\alpha }$- particle which are accelerated from rest by a potential difference of 100 V is

The fact that electric charges are integral multiples of the fundamental electronic charge was proved experimentally by 

The specific charge of an electron is 

The ratio of specific charge of an $\mathrm{\alpha }$-particle to that of a proton is 

Which of the following have the highest specific charge

For the Bohr's first orbit of circumference $2\mathrm{\pi r}$, the de-Broglie wavelength of revolving electron will be

According to de-Broglie, the de-Broglie wavelength for electron in an orbit of hydrogen atom is ${10}^{-10}$ m. The principle quantum number for this electron is $\left(r=5.13\times {10}^{-11}m\right)$

The energy of a photon of light with wavelength 5000 Å is approximately 2.5 eV. This way the energy of an X-ray photon with wavelength 1Å would be