12583 + Mcqs in Physics Page 61 McqOptions

3001.	Frequencies in the UHF range normally propagate by means of-
A.	Ground waves
B.	Sky waves.
C.	Surface waves
D.	Space waves
Answer» D. Space waves

Discussion

3002.	Which mode of communication is not employed for the transmission of T.V. signals?
A.	Ground wave propagation
B.	sky wave propagation
C.	space wave propagation
D.	None of these
Answer» B. sky wave propagation

Discussion

3003.	If the electron revolving around the nucleus in a radius 'r' with orbital speed 'v' has magnetic moment evr/2. Hence, using Bohr's postulate of the quantization of angular momentum obtain the magnetic moment (M) of hydrogen atom in its ground state and current (I) due to revolution of electron.
A.	\[M=\frac{eh}{4\pi m},I=\frac{eV}{2\pi r}\]
B.	\[M=\frac{2eh}{5\pi m},I=\frac{eV}{4\pi r}\]
C.	\[M=\frac{h}{\pi m},I=\frac{e}{\pi r}\]
D.	\[M=\frac{eh}{\pi m},I=\frac{eV}{\pi r}\]
Answer» B. \[M=\frac{2eh}{5\pi m},I=\frac{eV}{4\pi r}\]

Discussion

3004.	The ground state energy of hydrogen atom is -13.6 eV. If an electron makes a transition from an energy level - 0.85 eV to -1.51 eV, calculate the wavelength X of the spectral line emitted.
A.	\[1.88\times {{10}^{-6}}m\]
B.	\[1.87\times {{10}^{-10}}m\]
C.	\[1.66\times {{10}^{-9}}m\]
D.	\[2.36\times {{10}^{-9}}m\]
Answer» B. \[1.87\times {{10}^{-10}}m\]

Discussion

3005.	A Spectroscopic instrument can resolve two nearby wavelength \[\lambda \] and \[\lambda +\Delta \lambda \]if \[\lambda /\Delta \lambda \] is smaller than 8000. This is used to study the spectral lines of the Balmer series of hydrogen. Approximately how many lines will be resolved by the instrument?
A.	60
B.	43
C.	38
D.	21
Answer» D. 21

Discussion

3006.	The third line of the Balmer series spectrum of a hydrogen like ion of atomic number Z equals to 108.5 nm. Then Z is
A.	2
B.	5
C.	3
D.	6
Answer» B. 5

Discussion

3007.	If the series limit wavelength of Lyman series for the hydrogen atom is \[912\text{ }\overset{\text{o}}{\mathop{\text{A}}}\,\], then the series limit wavelength for Balmer series of hydrogen atoms is
A.	\[912\text{ }\overset{\text{o}}{\mathop{\text{A}}}\,\]
B.	\[912\text{ }\times \text{2}\overset{\text{o}}{\mathop{\text{A}}}\,\]
C.	\[912\text{ }\times 4\overset{\text{o}}{\mathop{\text{A}}}\,\]
D.	\[\frac{912}{2}\overset{\text{o}}{\mathop{\text{A}}}\,\]
Answer» D. \[\frac{912}{2}\overset{\text{o}}{\mathop{\text{A}}}\,\]

Discussion

3008.	The photon radiated from hydrogen corresponding to 2nd line of Lyman series is absorbed by a hydrogen like atom X in 2nd excited state. As a result the hydrogen like atom X makes a transition to nth orbit. Then -
A.	\[\text{X=H}{{\text{e}}^{\text{+}}},\,\,\text{n=4}\]
B.	\[X=L{{i}^{++}},\,\,n=6\]
C.	\[X=H{{e}^{+}},n=6\]
D.	\[X=L{{i}^{++}},n=9\]
Answer» E.

Discussion

3009.	When an electron in a hydrogen atom makes a transition from 2nd excited stated to ground state it emits a photon of frequency/ The frequency of photon emitted when an electron of \[L{{i}^{++}}\] makes transition from Ist excited state to ground state is
A.	\[\frac{243}{32}f\]
B.	\[\frac{141}{32}f\]
C.	\[\frac{81}{32}f\]
D.	\[\frac{63}{32}f\]
Answer» B. \[\frac{141}{32}f\]

Discussion

3010.	One of the lines in the emission spectrum of \[L{{i}^{2+}}\] has the same wavelength as that of the 2nd line of Balmer series in hydrogen spectrum. The electronic transition corresponding to this line is
A.	\[n=4\to n=2\]
B.	\[n=8\to n=2\]
C.	\[n=8\to n=4\]
D.	\[n=12\to n=6.3\]
Answer» E.

Discussion

3011.	Hydrogen atom excites energy level from fundamental state to n=3. Number of spectral lines according to Bohr, is
A.	4
B.	3
C.	1
D.	2
Answer» C. 1

Discussion

3012.	In Rutherford's experiment, the number of \[\alpha \]- particles scattered through an angle of \[60{}^\circ \]by a silver foil is 200 per minute. When the silver foil is replaced by a copper foil of the same thickness, the number of \[\alpha \]-particles scattered through an angle of \[60{}^\circ \] per minute is:
A.	\[\frac{200\times {{Z}_{Cu}}}{{{Z}_{Ag}}}\]
B.	\[200\times {{\left( \frac{{{Z}_{Cu}}}{{{Z}_{Ag}}} \right)}^{2}}\]
C.	\[200\times \frac{{{Z}_{Cu}}}{{{Z}_{Ag}}}\]
D.	\[200\times {{\left( \frac{{{Z}_{Ag}}}{{{Z}_{Cu}}} \right)}^{2}}\]
Answer» C. \[200\times \frac{{{Z}_{Cu}}}{{{Z}_{Ag}}}\]

Discussion

3013.	A 12.5 eV electron beam is used to bombard gaseous hydrogen at room temperature. Hydrogen atoms would be excited up to nth energy level the hence the wavelength obtained first member of Balmer series is\[{{\lambda }_{B}}\], then.
A.	\[{{\lambda }_{B}}=1415\overset{\text{o}}{\mathop{\text{A}}}\,\]
B.	\[{{\lambda }_{B}}=1215\overset{\text{o}}{\mathop{\text{A}}}\,\]
C.	\[{{\lambda }_{B}}=6563\overset{\text{o}}{\mathop{\text{A}}}\,\]
D.	\[{{\lambda }_{B}}=8523\overset{\text{o}}{\mathop{\text{A}}}\,\]
Answer» D. \[{{\lambda }_{B}}=8523\overset{\text{o}}{\mathop{\text{A}}}\,\]

Discussion

3014.	The energy of electron in the nth orbit of hydrogen atom is expressed as \[{{E}_{n}}=-\frac{13.6}{{{n}^{2}}}eV.\] The shortest and longest wavelength of Lyman series will be
A.	\[910\overset{\text{o}}{\mathop{\text{A}}}\,,\,\,1213\overset{\text{o}}{\mathop{\text{A}}}\,\]
B.	\[5463\overset{\text{o}}{\mathop{\text{A}}}\,,\,\,7858\overset{\text{o}}{\mathop{\text{A}}}\,\]
C.	\[1315\text{ }\overset{\text{o}}{\mathop{\text{A}}}\,,\text{ }1530\text{ }\overset{\text{o}}{\mathop{\text{A}}}\,~~\]
D.	None of these
Answer» B. \[5463\overset{\text{o}}{\mathop{\text{A}}}\,,\,\,7858\overset{\text{o}}{\mathop{\text{A}}}\,\]

Discussion

3015.	Taking Rydberg's constant \[R=1.097\times {{10}^{7}}m\], first and second wavelength of Balmer series in hydrogen spectrum is
A.	\[2000\text{ }\overset{\text{o}}{\mathop{\text{A }\!\!~\!\!\text{ }}}\,,\text{ }3000\text{ }\overset{\text{o}}{\mathop{\text{A }\!\!~\!\!\text{ }}}\,~\]
B.	\[\text{1575 }\overset{\text{o}}{\mathop{\text{A }\!\!~\!\!\text{ }}}\,\text{, }\!\!~\!\!\text{ 2960 }\overset{\text{o}}{\mathop{\text{A }\!\!~\!\!\text{ }}}\,\]
C.	\[\text{6529 }\overset{\text{o}}{\mathop{\text{A}}}\,\text{, }\,\text{4280 }\overset{\text{o}}{\mathop{\text{A }\!\!~\!\!\text{ }}}\,\]
D.	\[6552\text{ }\overset{\text{o}}{\mathop{\text{A }\!\!~\!\!\text{ }}}\,,\text{ }4863\text{ }\overset{\text{o}}{\mathop{\text{A }\!\!~\!\!\text{ }}}\,~~\]
Answer» E.

Discussion

3016.	When a gas of hydrogen-like ions is prepared in a particular excited state X. It emits photons having wavelength equal to the wavelength of the first line of the Lyman series together with photons of five other wavelengths Identify the gas and find the principal quantum number of the state X respectively.
A.	\[H{{e}^{+}},4\]
B.	\[L{{i}^{++}},3\]
C.	\[{{H}^{+}},2\]
D.	None of these
Answer» B. \[L{{i}^{++}},3\]

Discussion

3017.	The first member of Balmer series of hydrogen has a wavelength of \[6563\text{ }\overset{{}^\circ }{\mathop{A}}\,\] the wavelength of its second member will be
A.	\[4861\text{ }\overset{{}^\circ }{\mathop{\text{A}}}\,\]
B.	\[6563\text{ }\overset{{}^\circ }{\mathop{\text{A}}}\,\]
C.	\[3561\overset{{}^\circ }{\mathop{\text{A}}}\,\]
D.	\[1215\overset{{}^\circ }{\mathop{\text{A}}}\,\]
Answer» B. \[6563\text{ }\overset{{}^\circ }{\mathop{\text{A}}}\,\]

Discussion

3018.	In hydrogen spectrum the wavelength of \[{{H}_{\alpha }}\] line is 656 nm, whereas in the spectrum of a distant galaxy, \[{{H}_{\alpha }}\] line wavelength is 706 nm. Estimated speed of the galaxy with respect to earth is,
A.	\[2\times {{10}^{8}}m/s\]
B.	\[2\times {{10}^{7}}m/s\]
C.	\[2\times {{10}^{6}}m/s\]
D.	\[2\times {{10}^{5}}m/s\]
Answer» C. \[2\times {{10}^{6}}m/s\]

Discussion

3019.	The ratio of minimum to maximum wavelengths of radiation that an excited electron in a hydro- gen atom can emit while going to the ground state is
A.	1/2
B.	Zero
C.	3/4
D.	27/32
Answer» D. 27/32

Discussion

3020.	Whenever a photon is emitted by hydrogen in Balmer series, it is followed by another photon in Lyman series What wavelength does this latter photon correspond to?
A.	\[122\text{ }nm\]
B.	\[221\text{ }A{}^\circ \]
C.	\[\,321\text{ }nm\]
D.	\[111\text{ }A{}^\circ \]
Answer» B. \[221\text{ }A{}^\circ \]

Discussion

3021.	The difference between the longest wavelength line of the Balmer series and shortest wavelength line of the Lyman series for a hydrogenic atom (atomic number Z) equal to\[\Delta \lambda \]. The value of the Rydberg constant for the given atom is :
A.	\[\frac{5}{31}\frac{1}{\Delta \lambda .{{Z}^{2}}}\]
B.	\[\frac{5}{36}\frac{{{Z}^{2}}}{\Delta \lambda .}\]
C.	\[\frac{31}{5}\frac{1}{\Delta \lambda .{{Z}^{2}}}\]
D.	none of these
Answer» D. none of these

Discussion

3022.	The acceleration of an electron in the first orbit of the hydrogen atom (z=1) is:
A.	\[\frac{{{h}^{2}}}{{{\pi }^{2}}{{m}^{2}}{{r}^{3}}}\]
B.	\[\frac{{{h}^{2}}}{8{{\pi }^{2}}{{m}^{2}}{{r}^{3}}}\]
C.	\[\frac{{{h}^{2}}}{4{{\pi }^{2}}{{m}^{2}}{{r}^{3}}}\]
D.	\[\frac{{{h}^{2}}}{4\pi {{m}^{2}}{{r}^{3}}}\]
Answer» D. \[\frac{{{h}^{2}}}{4\pi {{m}^{2}}{{r}^{3}}}\]

Discussion

3023.	A Spectroscopic instrument can resolve two nearby wavelength \[\lambda \] and \[\lambda +\Delta \lambda \] if \[\lambda /\Delta \lambda \] is smaller than 8000. This is used to study the spectral lines of the Balmer series of hydrogen. Approximately how many lines will be resolved by the instrument?
A.	60
B.	43
C.	38
D.	21
Answer» D. 21

Discussion

3024.	The ratio of frequencies of the shortest wavelengths of Balmer and Lyman series of hydrogen atom is
A.	4 : 1
B.	1 : 4
C.	27 : 5
D.	5 : 27
Answer» B. 1 : 4

Discussion

3025.	The ionization potential of H-atom is 13.6 V. When it is excited from ground state by monochromatic radiations of 970.6 A, the number of emission lines will be (according to Bohr's theory)
A.	10
B.	8
C.	6
D.	4
Answer» D. 4

Discussion

3026.	One of the lines in the emission spectrum of \[L{{i}^{2+}}\] has the same wavelength as that of the Ist line of Lyman series in hydrogen spectrum. The electronic transition corresponding to this line is \[n=6\to 3=x\] Find the value of x.
A.	8
B.	3
C.	7
D.	5
Answer» C. 7

Discussion

3027.	The transition from the state n=4 to n=3 in a hydrogen-like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition
A.	\[2\to 1\]
B.	\[3\,\to 2\,\]
C.	\[4\to 2\]
D.	\[5\to 2\]
Answer» E.

Discussion

3028.	In the hydrogen atom spectrum \[{{\lambda }_{3-1}}\] and \[{{\lambda }_{2-1}}\] represent wavelengths emitted due to transition from second and first excited states to the ground. state respectively. The value of \[\frac{{{\lambda }_{3-1}}}{{{\lambda }_{2-1}}}\]is
A.	27/32
B.	32/27
C.	4/9
D.	9/4
Answer» B. 32/27

Discussion

3029.	The wavelength of radiation is \[{{\lambda }_{0}}\] when an electron jumps from third to second orbit of hydrogen atom. For the electron to jump from the fourth to the second orbit of the hydrogen atom, he wavelength of radiation emitted will be
A.	\[\frac{16}{25}{{\lambda }_{0}}\]
B.	\[\frac{20}{27}{{\lambda }_{0}}\]
C.	\[\frac{27}{20}{{\lambda }_{0}}\]
D.	\[\frac{25}{16}{{\lambda }_{0}}\]
Answer» C. \[\frac{27}{20}{{\lambda }_{0}}\]

Discussion

3030.	A neutron of kinetic energy 65eV collides in elastically with a singly ionized helium atom at rest. It is scattered at an angle of \[90{}^\circ \]with respect of its original direction. If the atom get de-excited subsequently by emitting radiation, then the impossible frequency of the emitted radiation is [Given: Mass of \[He\]atom = 4\[\times \](mass of neutron), Ionization energy of atom =13.6eV]
A.	\[1.82\times {{10}^{15}}Hz\]
B.	\[6.11\times {{10}^{15}}Hz\]
C.	\[11.67\times {{10}^{15}}Hz\]
D.	\[9.84\times {{10}^{15}}Hz\]
Answer» C. \[11.67\times {{10}^{15}}Hz\]

Discussion

3031.	The ionization energy of a hydrogen like Bohr atom is 4 Rydbergs. Find the wavelength of the radiation emitted when the electron jumps from the first excited state to the ground state
A.	\[300A{}^\circ \]
B.	\[2.5\times {{10}^{-11}}m\]
C.	\[100A{}^\circ \]
D.	\[1.5\times {{10}^{-11}}m\]
Answer» B. \[2.5\times {{10}^{-11}}m\]

Discussion

3032.	If one were to apply Bohr model to a particle of mass 'm' and charge 'q' moving in a plane under the influence of a magnetic field 'B', the energy of the charged particle in the nth level will be:
A.	\[n\left( \frac{hqB}{2\pi m} \right)\]
B.	\[n\left( \frac{hqB}{8\pi m} \right)\]
C.	\[n\left( \frac{hqB}{4\pi m} \right)\]
D.	\[n\left( \frac{hqB}{\pi m} \right)\]
Answer» D. \[n\left( \frac{hqB}{\pi m} \right)\]

Discussion

3033.	Electrons in hydrogen like atom (Z=3) make transitions from the fifth to the fourth orbit and from the fourth to the third orbit. The resulting radiations are incident normally on a metal plate and eject photoelectrons. The stopping potential for the photoelectrons ejected by the shorter wavelength is 3.95 volts. Find the stopping potential for the photoelectrons ejected by the longer wavelength, then. (Rydberg constant)
A.	5V
B.	2V
C.	0.754 V
D.	2.99V
Answer» D. 2.99V

Discussion

3034.	In an experiment on photoelectric effect photons of wavelength 300 nm eject electrons from a metal of work function 2.25eV. A photon of energy equal to that of the most energetic electron corresponds to the following transition in the hydrogen atom:
A.	n=2 to n=1 state.
B.	n=3 to n=1 state.
C.	n=3 to n=2 state.
D.	n=4 to n=3 state.
Answer» D. n=4 to n=3 state.

Discussion

3035.	Ultraviolet light of wavelengths \[{{\lambda }_{1}}\] and \[{{\lambda }_{2}}\] when allowed to fall on hydrogen atoms in their ground state is found to liberate electrons with kinetic energy \[K.{{E}_{1}}\] and \[K.{{E}_{2}}\] respectively. Find the value of Planck's constant.
A.	\[h=\left\| \frac{\left( K.{{E}_{2}}-K.{{E}_{1}} \right)\left( {{\lambda }_{1}}+{{\lambda }_{2}} \right)}{C\left( {{\lambda }_{1}}-{{\lambda }_{2}} \right)} \right\|\]
B.	\[h=\left\| \frac{\left( K.{{E}_{1}}-K.{{E}_{2}} \right)\left( {{\lambda }_{2}}-{{\lambda }_{1}} \right)}{C{{\lambda }_{1}}{{\lambda }_{2}}} \right\|\]
C.	\[h=\left\| \frac{\left( K.{{E}_{1}}-K.{{E}_{2}} \right){{\lambda }_{1}}{{\lambda }_{2}}}{C\left( {{\lambda }_{2}}-{{\lambda }_{1}} \right)} \right\|\]
D.	None of These
Answer» D. None of These

Discussion

3036.	Some energy levels of a molecule are shown in the figure. The ratio of the wavelengths \[r={{\lambda }_{1}}/{{\lambda }_{2}},\] is given by
A.	\[r=\frac{3}{4}\]
B.	\[r=\frac{1}{3}\]
C.	\[r=\frac{4}{3}\]
D.	\[r=\frac{2}{3}\]
Answer» C. \[r=\frac{4}{3}\]

Discussion

3037.	A diatomic molecule is made of two masses \[{{m}_{1}}\] and \[{{m}_{2}}\] which are separated by a distance r. If we calculate its rotational energy by applying Bohr's rule of angular momentum quantization, its energy will be given by: (n is an integer)
A.	\[\frac{{{\left( {{m}_{1}}+{{m}_{2}} \right)}^{2}}{{n}^{2}}{{h}^{2}}}{2m_{1}^{2}m_{2}^{2}{{r}^{2}}}\]
B.	\[\frac{{{n}^{2}}{{h}^{2}}}{2\left( {{m}_{1}}+{{m}_{2}} \right){{r}^{2}}}\]
C.	\[\frac{2{{n}^{2}}{{h}^{2}}}{\left( {{m}_{1}}+{{m}_{2}} \right){{r}^{2}}}\]
D.	\[\frac{\left( {{m}_{1}}+{{m}_{2}} \right){{n}^{2}}{{h}^{2}}}{2{{m}_{1}}{{m}_{2}}{{r}^{2}}}\]
Answer» E.

Discussion

3038.	As an electron makes a transition from an excited state to the ground state of a hydrogen - like atom/ion:
A.	kinetic energy decreases, potential energy increases but total energy remains same
B.	kinetic energy and total energy decrease but potential energy increases
C.	its kinetic energy increases but potential energy and total energy decrease
D.	kinetic energy, potential energy and total energy decrease
Answer» D. kinetic energy, potential energy and total energy decrease

Discussion

3039.	Hydrogen atom is excited from ground state to another state with principal quantum number equal to 4. Then the number of spectral lines in the emission spectra will be:
A.	2
B.	3
C.	5
D.	6
Answer» E.

Discussion

3040.	Hydrogen \[{{(}_{1}}{{H}^{1}})\], Deuterium \[{{(}_{1}}{{H}^{2}})\], singly ionized Helium \[{{{{(}_{2}}{{H}^{4}})}^{+}}\] and doubly ionized lithium \[{{{{(}_{3}}L{{i}^{6}})}^{++}}\] all have one electron around the nucleus. Consider an electron transition from n=2 to n=1. If the wavelengths of emitted radiation are \[{{\lambda }_{1}},{{\lambda }_{2}},{{\lambda }_{3}}\text{ and }{{\lambda }_{4}}\] respectively then approximately which one of the following is correct?
A.	\[4{{\lambda }_{1}}=2{{\lambda }_{2}}=2{{\lambda }_{3}}={{\lambda }_{4}}\]
B.	\[{{\lambda }_{1}}=2{{\lambda }_{2}}=2{{\lambda }_{3}}={{\lambda }_{4}}\]
C.	\[{{\lambda }_{1}}={{\lambda }_{2}}=4{{\lambda }_{3}}=9{{\lambda }_{4}}\]
D.	\[{{\lambda }_{1}}=2{{\lambda }_{2}}=3{{\lambda }_{3}}=4{{\lambda }_{4}}\]
Answer» D. \[{{\lambda }_{1}}=2{{\lambda }_{2}}=3{{\lambda }_{3}}=4{{\lambda }_{4}}\]

Discussion

3041.	Energy required for the electron excitation in \[L{{i}^{+}}\] from the first to the third Bohr orbit is:
A.	36.3 eV
B.	108.8 eV
C.	122.4eV
D.	12.1 eV
Answer» C. 122.4eV

Discussion

3042.	The energy of an electron in an excited hydrogen atom is -3.4 eV. Then, according to Bohr's theory, the angular momentum of this electron, in Js, is
A.	\[2.11\times {{10}^{-34}}\]
B.	\[3\times {{10}^{-34}}\]
C.	\[1.055\times {{10}^{-34}}\]
D.	\[0.5\times {{10}^{-34}}\,\]
Answer» B. \[3\times {{10}^{-34}}\]

Discussion

3043.	In a hypothetical system, a particle of mass m and charge -3q is moving around a very heavy particle charge q. Assume that Bohr's model is applicable to this system, then velocity of mass m in the first orbit is
A.	\[\frac{3{{q}^{2}}}{2{{\varepsilon }_{0}}h}\]
B.	\[\frac{3{{q}^{2}}}{4{{\varepsilon }_{0}}h}\]
C.	\[\frac{3q}{2\pi {{\varepsilon }_{0}}h}\]
D.	\[\frac{3q}{4\pi {{\varepsilon }_{0}}h}\]
Answer» B. \[\frac{3{{q}^{2}}}{4{{\varepsilon }_{0}}h}\]

Discussion

3044.	If potential energy between a proton and an electron is given by \[\|U\|=k{{e}^{2}}/2{{R}^{3}}\], where K is the charge of electron and R is the radius of atom, then radius of Bohr's orbit is given by (h = Planck's constant, k=constant)
A.	\[\frac{k{{e}^{2}}m}{{{h}^{2}}}\]
B.	\[\frac{6{{\pi }^{2}}}{{{n}^{2}}}\frac{k{{e}^{2}}m}{{{h}^{2}}}\]
C.	\[\frac{2\pi }{n}\frac{k{{e}^{2}}m}{{{h}^{2}}}\]
D.	\[\frac{4{{\pi }^{2}}k{{e}^{2}}m}{{{n}^{2}}{{h}^{2}}}\]
Answer» C. \[\frac{2\pi }{n}\frac{k{{e}^{2}}m}{{{h}^{2}}}\]

Discussion

3045.	The energy of a hydrogen atom in the first excited state if the potential energy is taken to be zero in the ground state.
A.	23.8 eV
B.	50.2 eV
C.	10.3 eV
D.	6.3 eV
Answer» B. 50.2 eV

Discussion

3046.	Suppose potential energy between electron and proton at separation r is given by U= K In (r), where K is a constant. For such a hypothetical hydrogen atom, the ratio of energy difference between energy levels (n=1 and n=2) and (n and n=4) is
A.	1
B.	2
C.	3
D.	4
Answer» B. 2

Discussion

3047.	In Rutherford scattering experiment, the number of a-particles scattered at \[60{}^\circ \] is \[5\times {{10}^{6}}\]. The number of a-particles scattered at \[120{}^\circ \] will be
A.	\[15\times {{10}^{6}}\]
B.	\[\frac{3}{5}\times {{10}^{6}}\]
C.	\[\frac{5}{9}\times {{10}^{6}}\]
D.	None of these
Answer» D. None of these

Discussion

3048.	An \[\alpha \]-particle of 10 MeV collides head-on with a copper nucleus (Z=29) and is deflected back. Then, the minimum distance of approach between the centers of the two is:
A.	\[8.4\times {{10}^{-15}}cm\]
B.	\[8.4\times {{10}^{-15}}m\]
C.	\[4.2\times {{10}^{-15}}m\]
D.	\[4.2\times {{10}^{-15}}cm\]
Answer» C. \[4.2\times {{10}^{-15}}m\]

Discussion

3049.	The ionization energy of a hydrogen-like Bohr atom is 4 Rydbergs. Find the wavelength of radiation emitted when the electron jumps from the first excited state to the ground state: [1 Rydberg \[=2.2\times {{10}^{-18}},h=6.6\times {{10}^{-34}}Js,\] \[c=3\times {{10}^{8}}m/s\]. Bohr radius of hydrogen atom \[=5\times {{10}^{-11}}m\]
A.	\[400\overset{\text{o}}{\mathop{\text{A}}}\,\]
B.	\[300\overset{\text{o}}{\mathop{\text{A}}}\,\]
C.	\[500\overset{\text{o}}{\mathop{\text{A}}}\,\]
D.	\[600\overset{\text{o}}{\mathop{\text{A}}}\,\]
Answer» C. \[500\overset{\text{o}}{\mathop{\text{A}}}\,\]

Discussion

3050.	In Bohr theory of hydrogen atom, let r, v and E be the radius of orbit, speed of electron and the total energy of the electron respectively. Which of the following quantities is proportional to the quantum number n?
A.	vr
B.	rE
C.	r/E
D.	r/v
Answer» B. rE

Discussion

Explore topic-wise MCQs in Joint Entrance Exam - Main (JEE Main).

Frequencies in the UHF range normally propagate by means of-

Which mode of communication is not employed for the transmission of T.V. signals?

If the electron revolving around the nucleus in a radius 'r' with orbital speed 'v' has magnetic moment evr/2. Hence, using Bohr's postulate of the quantization of angular momentum obtain the magnetic moment (M) of hydrogen atom in its ground state and current (I) due to revolution of electron.

The ground state energy of hydrogen atom is -13.6 eV. If an electron makes a transition from an energy level - 0.85 eV to -1.51 eV, calculate the wavelength X of the spectral line emitted.

A Spectroscopic instrument can resolve two nearby wavelength \[\lambda \] and \[\lambda +\Delta \lambda \]if \[\lambda /\Delta \lambda \] is smaller than 8000. This is used to study the spectral lines of the Balmer series of hydrogen. Approximately how many lines will be resolved by the instrument?

The third line of the Balmer series spectrum of a hydrogen like ion of atomic number Z equals to 108.5 nm. Then Z is

If the series limit wavelength of Lyman series for the hydrogen atom is \[912\text{ }\overset{\text{o}}{\mathop{\text{A}}}\,\], then the series limit wavelength for Balmer series of hydrogen atoms is

The photon radiated from hydrogen corresponding to 2nd line of Lyman series is absorbed by a hydrogen like atom X in 2nd excited state. As a result the hydrogen like atom X makes a transition to nth orbit. Then -

When an electron in a hydrogen atom makes a transition from 2nd excited stated to ground state it emits a photon of frequency/ The frequency of photon emitted when an electron of \[L{{i}^{++}}\] makes transition from Ist excited state to ground state is

One of the lines in the emission spectrum of \[L{{i}^{2+}}\] has the same wavelength as that of the 2nd line of Balmer series in hydrogen spectrum. The electronic transition corresponding to this line is

Hydrogen atom excites energy level from fundamental state to n=3. Number of spectral lines according to Bohr, is

A 12.5 eV electron beam is used to bombard gaseous hydrogen at room temperature. Hydrogen atoms would be excited up to nth energy level the hence the wavelength obtained first member of Balmer series is\[{{\lambda }_{B}}\], then.

The energy of electron in the nth orbit of hydrogen atom is expressed as \[{{E}_{n}}=-\frac{13.6}{{{n}^{2}}}eV.\] The shortest and longest wavelength of Lyman series will be

Taking Rydberg's constant \[R=1.097\times {{10}^{7}}m\], first and second wavelength of Balmer series in hydrogen spectrum is

The first member of Balmer series of hydrogen has a wavelength of \[6563\text{ }\overset{{}^\circ }{\mathop{A}}\,\] the wavelength of its second member will be

In hydrogen spectrum the wavelength of \[{{H}_{\alpha }}\] line is 656 nm, whereas in the spectrum of a distant galaxy, \[{{H}_{\alpha }}\] line wavelength is 706 nm. Estimated speed of the galaxy with respect to earth is,

The ratio of minimum to maximum wavelengths of radiation that an excited electron in a hydro- gen atom can emit while going to the ground state is

Whenever a photon is emitted by hydrogen in Balmer series, it is followed by another photon in Lyman series What wavelength does this latter photon correspond to?

The difference between the longest wavelength line of the Balmer series and shortest wavelength line of the Lyman series for a hydrogenic atom (atomic number Z) equal to\[\Delta \lambda \]. The value of the Rydberg constant for the given atom is :

The acceleration of an electron in the first orbit of the hydrogen atom (z=1) is:

The ratio of frequencies of the shortest wavelengths of Balmer and Lyman series of hydrogen atom is

The ionization potential of H-atom is 13.6 V. When it is excited from ground state by monochromatic radiations of 970.6 A, the number of emission lines will be (according to Bohr's theory)

One of the lines in the emission spectrum of \[L{{i}^{2+}}\] has the same wavelength as that of the Ist line of Lyman series in hydrogen spectrum. The electronic transition corresponding to this line is \[n=6\to 3=x\] Find the value of x.

The transition from the state n=4 to n=3 in a hydrogen-like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition

In the hydrogen atom spectrum \[{{\lambda }_{3-1}}\] and \[{{\lambda }_{2-1}}\] represent wavelengths emitted due to transition from second and first excited states to the ground. state respectively. The value of \[\frac{{{\lambda }_{3-1}}}{{{\lambda }_{2-1}}}\]is

The wavelength of radiation is \[{{\lambda }_{0}}\] when an electron jumps from third to second orbit of hydrogen atom. For the electron to jump from the fourth to the second orbit of the hydrogen atom, he wavelength of radiation emitted will be

The ionization energy of a hydrogen like Bohr atom is 4 Rydbergs. Find the wavelength of the radiation emitted when the electron jumps from the first excited state to the ground state

If one were to apply Bohr model to a particle of mass 'm' and charge 'q' moving in a plane under the influence of a magnetic field 'B', the energy of the charged particle in the nth level will be:

In an experiment on photoelectric effect photons of wavelength 300 nm eject electrons from a metal of work function 2.25eV. A photon of energy equal to that of the most energetic electron corresponds to the following transition in the hydrogen atom:

Ultraviolet light of wavelengths \[{{\lambda }_{1}}\] and \[{{\lambda }_{2}}\] when allowed to fall on hydrogen atoms in their ground state is found to liberate electrons with kinetic energy \[K.{{E}_{1}}\] and \[K.{{E}_{2}}\] respectively. Find the value of Planck's constant.

Some energy levels of a molecule are shown in the figure. The ratio of the wavelengths \[r={{\lambda }_{1}}/{{\lambda }_{2}},\] is given by

A diatomic molecule is made of two masses \[{{m}_{1}}\] and \[{{m}_{2}}\] which are separated by a distance r. If we calculate its rotational energy by applying Bohr's rule of angular momentum quantization, its energy will be given by: (n is an integer)

As an electron makes a transition from an excited state to the ground state of a hydrogen - like atom/ion:

Hydrogen atom is excited from ground state to another state with principal quantum number equal to 4. Then the number of spectral lines in the emission spectra will be:

Energy required for the electron excitation in \[L{{i}^{+}}\] from the first to the third Bohr orbit is:

The energy of an electron in an excited hydrogen atom is -3.4 eV. Then, according to Bohr's theory, the angular momentum of this electron, in Js, is

In a hypothetical system, a particle of mass m and charge -3q is moving around a very heavy particle charge q. Assume that Bohr's model is applicable to this system, then velocity of mass m in the first orbit is

If potential energy between a proton and an electron is given by \[|U|=k{{e}^{2}}/2{{R}^{3}}\], where K is the charge of electron and R is the radius of atom, then radius of Bohr's orbit is given by (h = Planck's constant, k=constant)

The energy of a hydrogen atom in the first excited state if the potential energy is taken to be zero in the ground state.

Suppose potential energy between electron and proton at separation r is given by U= K In (r), where K is a constant. For such a hypothetical hydrogen atom, the ratio of energy difference between energy levels (n=1 and n=2) and (n and n=4) is

In Rutherford scattering experiment, the number of a-particles scattered at \[60{}^\circ \] is \[5\times {{10}^{6}}\]. The number of a-particles scattered at \[120{}^\circ \] will be

An \[\alpha \]-particle of 10 MeV collides head-on with a copper nucleus (Z=29) and is deflected back. Then, the minimum distance of approach between the centers of the two is:

In Bohr theory of hydrogen atom, let r, v and E be the radius of orbit, speed of electron and the total energy of the electron respectively. Which of the following quantities is proportional to the quantum number n?