Mere Teacher

Set 8 of 16 · Questions 211-240 of 453

In the print window choose “Save as PDF”. The file prints without a web address or date line.

Mere Teacher · Previous Year Questions JEE Main Physics · Atoms · Set 8 (Q211-240)
Scan or visit mereteacher.com for free PYQ practice, timed CBT tests, step-by-step solutions and BroBot AI. Answers and solutions are free with a sign-up.
211. $An electron in an excited state of Li^{2 +} ion has angular momentum \frac{3 h}{2 π} . The de Broglie wavelength of electron in this state is Pπ a_{n} (where a_{0} = Bohr radius). The value of P is$ (1) $3$ (2) $2$ (3) $1$ (4) $4$ 212. $The mass number of nucleus having radius equal to half of the radius of nucleus with mass number 192 is:$ (1) $24$ (2) $32$ (3) $40$ (4) $20$ 213. $An electron is moving round the nucleus of a hydrogen atom in a circular orbit of radius r . The Coulomb force F between the two is (where K = \frac{1}{4 π ϵ _{0}})$ (1) $K \frac{e ^{2}}{r ^{2}} r$ (2) $- K \frac{e ^{2}}{r ^{2}} r$ (3) $K \frac{e ^{2}}{r ^{3}} r$ (4) $- K \frac{e ^{2}}{r ^{3}} r$ 214. $The total energy of an electron revolving in the second orbit of hydrogen atom is$ (1) $- 13.6 eV$ (2) $- 1.51 eV$ (3) $- 3.4 eV$ (4) $zero$ 215. $If an electron in a hydrogen atom jumps from the 3^{rd} orbit to the 2^{nd} orbit, it emits a photon of wavelength λ . When it jumps from the 4^{th} orbit to the 3^{rd} orbit, the corresponding wavelength of the photon will be$ (1) $\frac{16}{25} λ$ (2) $\frac{9}{16} λ$ (3) $\frac{20}{7} λ$ (4) $\frac{20}{13} λ$ 216. $Hydrogen ion and singly ionized helium atom are accelerated, from rest, through the same potential difference. The ratio of final speeds of hydrogen and helium ions is close to$ (1) $02:01$ (2) $01:02$ (3) $10:07$ (4) $05:07$ 217. $In Bohr's theory of Hydrogen atom, the electron jumps from higher orbit n to lower orbit p . The wavelength will be minimum for the transition$ (1) $n = 5 to p = 4$ (2) $n = 4 to p = 3$ (3) $n = 3 to p = 2$ (4) $n = 2 to p = 1$ 218. $If an electron in hydrogen atom jumps from an orbit of level n = 3 to an orbit of level n = 2, the emitted radiation has a frequency (R = Rydberg constant, C = velocity of light)$ (1) $\frac{RC}{25}$ (2) $\frac{5 RC}{36}$ (3) $\frac{3 RC}{27}$ (4) $\frac{8 RC}{9}$ 219. $The potential difference that must be applied to stop the fastest photoelectrons emitted by a nickel surface, having work function 5.01 eV, when ultraviolet light of 200 nm falls on it, must be$ (1) $2.4 V$ (2) $-1.2 V$ (3) $- 2.4 V$ (4) $1.2 V$ 220. $An electron is moving in an orbit of a hydrogen atom from which there can be a maximum of six transitions. An electron is moving in an orbit of another hydrogen atom from which there can be a maximum of three transitions. The ratio of the velocity of the electron in these two orbits is$ (1) $½$ (2) $2/1$ (3) $5/4$ (4) $3/4$ 221. $If the series limit frequency of the Lyman series is v_{L}, then the series limit frequency of the Pfund series is :$ (1) $v_{L} /16$ (2) $v_{L} /25$ (3) $25 v_{L}$ (4) $16 v_{L}$ 222. $The half life of a radioactive substance is 20 minutes. The approximate time interval (t_{2} - t_{1}) between the time t_{2} when \frac{2}{3} of it has decayed and time t_{1} when \frac{1}{3} of it had decayed is:$ (1) $7 min$ (2) $14 min$ (3) $20 min$ (4) $28 min$ 223. $When a metallic surface is illuminated with radiation of wavelength λ the stopping potential is V. If the same surface is illuminated with radiation of wavelength 2 λ, the stopping potential is \frac{V}{4} . The threshold wavelength for the metallic surface is:$ (1) $3 λ$ (2) $4 λ$ (3) $5 λ$ (4) $\frac{5}{2} λ$ 224. $The centripetal acceleration ' a' of an electron in an orbit of hydrogen and the principal quantum number ' n' of the orbit are related by$ (1) $a \propto n^{2}$ (2) $a \propto \frac{1}{n ^{2}}$ (3) $a \propto n^{4}$ (4) $\propto \frac{1}{n ^{4}}$ 225. $Considering the Bohr model of hydrogen like atoms, the ratio of the radius of 5^{th} orbit of the electron in Li^{2 +} and He^{+} is$ (1) $\frac{3}{2}$ (2) $\frac{2}{3}$ (3) $\frac{4}{9}$ (4) $\frac{9}{4}$ 226. $Ratio of longest wavelength corresponding to Lyman and Balmer series in Hydrogen spectrum is$ (1) $\frac{7}{29}$ (2) $\frac{9}{31}$ (3) $\frac{5}{27}$ (4) $\frac{3}{23}$ 227. $A hydrogen atom in ground state is given an energy of 10.2 eV . How many spectral lines will be emitted due to transition of electrons?$ (1) $6$ (2) $3$ (3) $10$ (4) $1$ 228. $Taking the wavelength of first Balmer line in hydrogen spectrum (n = 3 to n = 2) as 660 nm, the wavelength of the 2ndBalmer line (n = 4 to n = 2) will be;$ (1) $889.2 nm$ (2) $488.9 nm$ (3) $642.7 nm$ (4) $388.9 nm$ 229. $Which of the following spectral series of hydrogen atom is lying in visible range of electromagnetic wave?$ (1) $Lyman series$ (2) $Paschen series$ (3) $Balmer series$ (4) $Pfund series$ 230. $The atomic hydrogen emits a line spectrum consisting of various series. Which series of hydrogen atomic spectra is lying in the visible region?$ (1) $Brackett series$ (2) $Paschen series$ (3) $Lyman series$ (4) $Balmer series$ 231. $The ionization energy of Li^{++} is equal to$ (1) $9 hcR$ (2) $6 hcR$ (3) $2 hcR$ (4) $hcR .$ 232. $The ratio of wavelengths of the last line of Balmer series and the last line of Lyman series is$ (1) $1$ (2) $4$ (3) $0.5$ (4) $2$ 233. $The angular momentum of the orbital electron is integral multiple of$ (1) $h$ (2) $2 πh$ (3) $\frac{h}{2 π}$ (4) $3 πh$ 234. $Estimate the approximate volume of aluminium nucleus (A = 27) Use (\frac{R _{0} ≃ 1.0 \times 10 ^{- 15} m}{π = 3})$ (1) $1 \times 10^{- 13} (Å)^{3}$ (2) $1 \times 10^{- 10} (Å)^{3}$ (3) $1 \times 10^{- 15} (Å)^{3}$ (4) $1 \times 10^{- 17} (Å)^{3}$ 235. $A hydrogen atom changes its state from n = 3 to n = 2 . Due to recoil, the percentage change in the wave length of emitted light is approximately 1 \times 10^{- n} . The value of n is_______. [Given Rhc = 13.6 eV, hc = 1242 eVnm, h = 6.6 \times 10^{- 34} J s mass of the hydrogenatom = 1.6 \times 10^{- 27} kg]$ 236. $An electron in the hydrogen atom initially in the fourth excited state makes a transition to n^{th} energy state by emitting a photon of energy 2.86 eV. The integer value of n will be _________.$ 237. $Hydrogen atom is bombarded with electrons accelerated through a potential different of V, which causes excitation of hydrogen atoms. If the experiment is being formed at T = 0 K . The minimum potential difference needed to observe any Balmer series lines in the emission spectra will be \frac{α}{10} V, where α = ---------$ 238. $The K_{α} X-ray of molybdenum has wavelength 0.071nm. If the energy of a molybdenum atoms with a K electron knocked out is 27.5kV, the energy of this atom when an L electron is knocked out will be keV. (Round off to the nearest integer) (h = 4.14 \times 1 0^{- 15} eVs, c = 3 \times 1 0^{8} m s^{- 1})$ 239. $A electron of hydrogen atom on an excited state is having energy E_{n} = - 0.85 eV . The maximum number of allowed transitions to lower energy level is\dots..$ 240. $A particular hydrogen - like ion emits the radiation of frequency 3 \times 10^{15} Hz when it makes transition from n = 2 to n = 1 . The frequency of radiation emitted in transition from n = 3 to n = 1 is \frac{x}{9} \times 10^{15} Hz, when x =$