If the wavelength of the first line of the Balmer series of hydrogen atom is 6561Å, the wavelength of the second line of the series should be

[A] 13122Å

[B] 3280Å

[C] 4860Å

[D] 2187Å

An electron makes a transition from orbit n =4 to the orbit n = 2 of a hydrogen atom. The wave number of the emitted radiations (R = Rydberg’s constant) will be

[A] \( \frac{16}{3R}\)

[B] \( \frac{2R}{16}\)

[C] \( \frac{3R}{16}\)

[D] \( \frac{4R}{16}\)

The wavelength of radiation emitted is λ_{0} when an electron jumps from the third to the second orbit of hydrogen atom. For the electron jump from the fourth to the second orbit [A] \( \frac{16}{25}\)λ_{0}

[B] \( \frac{20}{27}\)λ_{0}

[C] \( \frac{27}{20}\)λ_{0}

[D] \( \frac{25}{16}\)λ_{0}

When an electron in hydrogen atom is excited, from its 4th to 5th stationary orbit, the change in angular momentum of electron is (Planck’s constant h = 6.6×10^{-34} J-s)

[A] 4.16×10^{-34} J-s

[B] 3.32×10^{-34}J-s

[C] 1.05×10^{-34} J-s

[D] 2.08×10^{-34} J-s

The concept of stationary orbits was proposed by

[A] Neil Bohr

[B] J.J. Thomson

[C] Rutherford

[D] I. Newton

The ratio of the speed of the electrons in the ground state of hydrogen to the speed of light in vacuum is

[A] \( \frac{1}{2}\)

[B] \( \frac{2}{137}\)

[C] \( \frac{1}{137}\)

[D] \( \frac{1}{237}\)

The ionisation potential of H-atom is 13.6 V. When it is excited from ground state by monochromatic radiations of 970.6 Å, the number of emission lines will be (according to Bohr’s theory [A] 10

[B] 3

[C] 6

[D] 4

Excitation energy of a hydrogen like ion in its first excitation state is 40.8 eV. Energy needed to remove the electron from the ion in ground state is

[A] 54.4 eV

[B] 13.6 eV

[C] 40.8 eV

[D] 27.2 eV

In Bohr’s model, the atomic radius of the first orbit is r0 then the radius of the third orbit is

[A] r_{0}/9

[B] r_{0}

[C] 9r_{0}

[D] 3r_{0}

The frequency of Kα, Kβ and Lλ X-rays of material are γ_{1} γ_{2} and γ_{3} respectively. Which of the following relations holds good [A] \( γ_2=\sqrt{γ_1γ_3}\)

[B] \( γ_3= \sqrt{γ_1γ_2}\)

[C] \( γ_2= \frac{γ1+γ3}{2}\)

[D] \( γ_2=γ_1+γ_3 \)

When the electron in hydrogen atom jumps from the second orbit to the first orbit, the wavelength of the radiation emitted is λ When the electron jumps from the third to the first orbit, [A] \( \frac{9}{4}\)λ

[B] \( \frac{4}{9}\)λ

[C] \( \frac{27}{32}\)λ

[D] \( \frac{32}{27}\)λ

The ground state energy of hydrogen atom is – 1 3. 6eV.The kinetic energy of the electron in this state is

[A] 1.85eV

[B] 13.6 eV

[C] 6.8 eV

[D] 3.4 eV

Atomic hydrogen is excited from the ground state to the nth state. The number of lines in the emission spectrum will be

[A] \( \frac{n(n+1)}{2}\)

[B] \( \frac{n(n-1)}{2}\)

[C] \( \frac{(n-1)^2}{2}\)

[D] \( \frac{(n+1)^2}{2}\)

The difference in angular momentum associated with the electron in the two successive orbits of hydrogen atom is

[A] \( \frac{h}{π}\)

[B] \(\frac{h}{2π}\)

[C] \( \frac{h}{2}\)

[D] \((n-1)\frac{h}{2π}\)

The ratio of the largest to shortest wavelengths in Balmer series of hydrogen spectra is

[A] \( \frac{25}{9}\)

[B] \( \frac{17}{6}\)

[C] \(\frac{9}{5}\)

[D] \(\frac{5}{4}\)

In hydrogen atom, if the difference in the energy of the electron in n = 2 and n = 3 orbits is E, the ionization energy of hydrogen atom is

[A] 13. 2E

[B] 7.2E

[C] 5.6E

[D] 3.2E1

Which of the following is not correct in Bohr model of hydrogen atom?

[A] The radius of nth orbit is proportional to n^{2}

[B] The total energy of electron in n th orbit is proportional ton

[C] The angular momentum of an electron in an orbit is an integral multiple of\( \frac{h}{2π} \)

[D] The magnitude of the potential energy of an electron in any orbit is greater than its kinetic energy

If ω is the speed of electron in the nth orbit hydrogen atom, then

[A] ω ∝ n^{1/2}

[B] ω ∝ \(\frac{1}{n}\)

[C] ω ∝ \(\frac{1}{n^2}\)

[D] ω ∝\(\frac{1}{n^3}\)

# Modern Physics Mock Test-3

CategoriesNEET IIT Physics