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Set 5 of 14 · Questions 121-150 of 394

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Mere Teacher · Previous Year Questions NEET Physics · Atoms · Set 5 (Q121-150)
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121. $In accordance with the Bohr's model, the quantum number that characterises the Earth's revolution around the Sun in an orbit of radius 1.5 \times 10^{11} m with orbital speed 3 \times 10^{4} m s^{- 1} is [Given: mass of Earth = 6 \times 10^{24} kg]$ (1) $8.57 \times 10^{64}$ (2) $5.98 \times 10^{46}$ (3) $2.57 \times 10^{74}$ (4) $2.57 \times 10^{38}$ 122. $Hydrogen atom in the ground state absorbs Δ E amount of energy. If the orbital angular momentum of the electron is increased by \frac{h}{2 π} (h = Planck's constant), then the magnitude of Δ E is$ (1) $12.09 eV$ (2) $12.75 eV$ (3) $10.2 eV$ (4) $13.6 eV$ 123. $A proton and an α -particle, having kinetic energies K_{p} and K_{α} respectively, enter into a magnetic field atright angles. The ratio of the radii of trajectory of proton to that of α -particle is 2:1. The ratio of K_{p} : K_{α} is:$ (1) $1: 8$ (2) $8: 1$ (3) $1: 4$ (4) $4: 1$ 124. $An electron (mass m ) with initial velocity v = v_{0} i + v_{0} j is in an electric field E = - E_{0} k . If λ_{0} is initial de-Broglie wavelength of electron, its de-Broglie wave length at time t is given by :$ (1) $\frac{λ _{0}}{1 + \frac{e ^{2} E _{0}^{2} t ^{2}}{m ^{2} v _{0}^{2}}}$ (2) $\frac{λ _{0}}{1 + \frac{e ^{2} E ^{2} t ^{2}}{2 m ^{2} v _{0}^{2}}}$ (3) $\frac{λ _{0}}{2 + \frac{e ^{2} E ^{2} t ^{2}}{m ^{2} v _{0}^{2}}}$ (4) $\frac{λ _{0} 2}{1 + \frac{e ^{2} E ^{2} t ^{2}}{m ^{2} v _{0}^{2}}}$ 125. $A monochromatic radiation of wavelength λ is incident on a hydrogen sample in ground state. The sample subsequently emits radiation of six different wavelengths, then the value of λ is [Use ch = 1242 eV - m]$ (1) $80 nm$ (2) $85.5 nm$ (3) $97.4 nm$ (4) $100.2 nm$ 126. $In hydrogen spectrum, the shortest wavelength in the Balmer series is λ . The shortest wavelength in the Brackett series is [NEET 2023]$ (1) $4 λ$ (2) $9 λ$ (3) $16 λ$ (4) $2 λ$ 127. $When the energy of the incident radiation is increased by 20%, the kinetic energy of the photoelectrons emitted from a metal surface increased from emitted 0.5 eV to 0.8eV. The work function of the metal is:$ (1) $0.65 eV$ (2) $1.0 eV$ (3) $1.3 eV$ (4) $1.5 eV$ 128. $The total energy of an electron in the n th stationary orbit of the hydrogen atom can be obtained by [NEET 2020]$ (1) $E_{n} = \frac{13.6}{n ^{2}} eV$ (2) $E_{n} = - \frac{13.6}{n ^{2}} eV$ (3) $E_{n} = - \frac{1.36}{n ^{2}} eV$ (4) $E_{n} = - 13.6 \times n^{2} eV$ 129. $Consider an electron in a hydrogen atom, revolving in its second excited state (having radius 4.65 Å). The de-Broglie wavelength of this electron is:$ (1) $3.5 Å$ (2) $6.6 Å$ (3) $12.9 Å$ (4) $9.7 Å$ 130. $Arrange the following in the ascending order of wavelength (λ) : (A) Microwaves (λ_{1}) (B) Ultraviolet rays (λ_{2}) (C) Infrared rays (λ_{3}) (D) X-rays (λ_{4}) Choose the most appropriate answer from the options given below:$ (1) $λ_{4} < λ_{3} < λ_{2} < λ_{1}$ (2) $λ_{3} < λ_{4} < λ_{2} < λ_{1}$ (3) $λ_{4} < λ_{3} < λ_{1} < λ_{2}$ (4) $λ_{4} < λ_{2} < λ_{3} < λ_{1}$ 131. $If the series limit frequency of Balmer series is v_{B}, then the series limit frequency of the Brackett series is$ (1) $\frac{4 v _{B}}{25}$ (2) $\frac{v _{B}}{9}$ (3) $\frac{v _{B}}{4}$ (4) $\frac{9 v _{B}}{4}$ 132. $The interplanar distance in a crystal is 2.8 . The value of maximum wavelength which can be diffracted$ (1) $2.8 \times 1 0^{- 8} m$ (2) $5.6 \times 1 0^{- 8} m$ (3) $1.4 \times 1 0^{- 8} m$ (4) $7.6 \times 1 0^{- 8} m$ 133. $The activity of a radioactive material is 2.56 x 1 0^{- 3} Ci. If the half life of the material is 5 days, after how many days the activity will become 2 x 1 0^{- 5} Ci?$ (1) $30 days$ (2) $35 days$ (3) $40 days$ (4) $25 days$ 134. $In hydrogen atom spectrum, (R \to Rydberg's constant) (A) the maximum wavelength of the radiation of Lyman series is \frac{4}{3 R} (B) the Balmer series lies in the visible region of the spectrum (C) the minimum wavelength of the radiation of Paschen series is \frac{9}{R} (D) the minimum wavelength of Lyman series is \frac{5}{4 R} Choose the correct answer from the options given below:$ (1) $(B), (D) Only$ (2) $(A), (B) and (C) Only$ (3) $(A), (B) and (D) Only$ (4) $(A), (B) Only$ 135. $The radius of hydrogen atom in the ground state is 0.53 A . After collision with an electron it is found to have radius of 2.12Å, the principal quantum number ' n' of the final state of the atom is$ (1) $n = 3$ (2) $n = 1$ (3) $n = 4$ (4) $n = 2$ 136. $A hydrogen atom, initially in the ground state is excited by absorbing a photon of wavelength 980Å .The radius of the atom in the excited state, in terms of Bohr radius a_{0}, will be : (hc = 12500 eV- Å)$ (1) $16 a_{0}$ (2) $25 a_{0}$ (3) $9 a_{0}$ (4) $4 a_{0}$ 137. $In hydrogen atom, if an electron in the orbit with principal quantum number ' n' jumps to the first excited state, the wavelength of the emitted photon is ' λ'. Then the value of n is (R-Rydberg constant)$ (1) $\frac{4 λR}{λR + 4}$ (2) $\frac{4 λR}{λR - 4}$ (3) $\frac{λR - 4}{4 λR}$ (4) $\frac{λR + 4}{4 λR}$ 138. $The radius of inner most orbit of hydrogen atom is 5.3 \times 10^{- 11} m . What is the radius of third allowed orbit of hydrogen atom? [NEET 2023]$ (1) $1.06Å$ (2) $1.59Å$ (3) $4.77Å$ (4) $0.53Å$ 139. $The difference in the wavelength between the maximum and minimum of Balmer series [Use R_{H} = 1 \times 10^{7} m^{- 1}]$ (1) $1600Å$ (2) $3200Å$ (3) $4000Å$ (4) $4800Å$ 140. $A nucleus at rest disintegrates into two smaller nuclei with their masses in the ratio of 2 : 1 . After disintegration they will move:$ (1) $in the same direction with same speed.$ (2) $in opposite directions with the same speed.$ (3) $in opposite directions with speed in the ratio of 2 : 1 respectively.$ (4) $in opposite directions with speed in the ratio of 1 : 2 respectively.$ 141. $An electron & a photon have same energy E . Find the ratio of de Broglie wavelength of electron to wavelength of photon. Given mass of electron is m & speed of light is C.$ (1) $\frac{1}{C} (\frac{E}{2 m})^{\frac{1}{2}}$ (2) $(\frac{E}{m})^{\frac{1}{2}} C$ (3) $\frac{2 mE}{C}$ (4) $(\frac{E}{2 m})^{\frac{1}{2}}$ 142. $An electron is revolving in its Bohr orbit having Bohr radius of 0.529Å, then the radius of third orbit is$ (1) $4.761Å$ (2) $4234 nm$ (3) $5125 nm$ (4) $4496Å$ 143. $Consider 3^{rd} orbit of H e^{+} (Helium), using non‐relativistic approach, the speed of electron in this orbit will be [given K = 9 \times 1 0^{9} constant, Z = 2 and h (Planck’s Constant) = 6.6 \times 1 0^{- 34} Js]$ (1) $0.73 \times 1 0^{6} m / s$ (2) $3.0 \times 1 0^{8} m / s$ (3) $2.92 \times 1 0^{6} m / s$ (4) $1.46 \times 1 0^{6} m / s$ 144. $The de-Broglie wavelength associated with electron of hydrogen atom in the ground state is$ (1) $6.26Å$ (2) $10Å$ (3) $0.3Å$ (4) $3.3Å$ 145. $The wavelength λ_{e} of an electron and λ_{p} of a photon of same energy E are related by:$ (1) $λ_{p} \propto λ_{e}$ (2) $λ_{p} \propto λ_{e}$ (3) $λ_{p} \propto \frac{1}{λ _{e}}$ (4) $λ_{p} \propto λ_{e}^{2}$ 146. $If an electron is moving in the n^{th} orbit of the hydrogen atom, then its velocity (v_{n}) for the n^{th} orbit is given as:$ (1) $v_{n} \propto n$ (2) $v_{n} \propto \frac{1}{n}$ (3) $v_{n} \propto n^{2}$ (4) $v_{n} \propto \frac{1}{n ^{2}}$ 147. $A particle of mass m moves in a circular orbit in a central potential field U (r) = \frac{1}{2} k r^{2} . If Bohr’s quantization conditions are applied, radii of possible orbitls and energy levels vary with quantum number n as:$ (1) $r_{n} \propto n, E_{n} \propto n$ (2) $r_{n} \propto n, E_{n} \propto \frac{1}{n}$ (3) $r_{n} \propto n, E_{n} \propto n$ (4) $r_{n} \propto n^{2}, E_{n} \propto \frac{1}{n ^{2}}$ 148. $The longest wavelength associated with Paschen series is: (Given R_{H} = 1.097 \times 10^{7} SI unit)$ (1) $3.646 \times 10^{- 6} m$ (2) $1.876 \times 10^{- 6} m$ (3) $2.973 \times 10^{- 6} m$ (4) $1.094 \times 10^{- 6} m$ 149. $The ratio of maximum to minimum wavelength in Balmer series of an hydrogenic atom is$ (1) $\frac{9}{5}$ (2) $\frac{12}{7}$ (3) $\frac{9}{7}$ (4) $\frac{14}{9}$ 150. $The anode voltage of a photocell is kept fixed. The wavelength λ of the light falling on the cathode is gradually changed. The plate current I of the photocell varies as follows : (Assume that rate of photon falling is maintained constant)$ (1) (2) (3) (4)