12583 + Mcqs in Physics Page 62 McqOptions

3051.	Excitation energy of a hydrogen like ion in its excitation state is 40.8 eV. Energy needed to remove the electron from the ion in ground state is
A.	54.4 eV
B.	13.6eV
C.	40.8 eV
D.	27.2 eV
Answer» B. 13.6eV

Discussion

3052.	If the atom \[_{100}F{{m}^{257}}\] follows the Bohr model and the radius of \[_{100}F{{m}^{257}}\] is n times the Bohr radius, then find n.
A.	100
B.	200
C.	4
D.	¼
Answer» E.

Discussion

3053.	In Rutherford scattering experiment, what will be the correct angle for a-scattering for an impact parameter, b=0?
A.	\[90{}^\circ \]
B.	\[270{}^\circ \]
C.	\[0{}^\circ \]
D.	\[180{}^\circ \]
Answer» E.

Discussion

3054.	Electrons are bombarded to excite hydrogen atoms and six spectral lines are observed. If \[{{E}_{g}}\] is the ground state energy of hydrogen, the minimum energy the bombarding electrons should posses is
A.	\[\frac{8{{E}_{g}}}{9}\]
B.	\[\frac{15{{E}_{g}}}{16}\]
C.	\[\frac{35{{E}_{g}}}{36}\]
D.	\[\frac{48{{E}_{g}}}{49}\]
Answer» C. \[\frac{35{{E}_{g}}}{36}\]

Discussion

3055.	In the Rutherford experiment, a-particles are scattered from a nucleus as shown. Out of the four paths, which path is not possible?
A.	D
B.	B
C.	C
D.	A
Answer» D. A

Discussion

3056.	The element which has a \[{{K}_{\alpha }}\] x-rays line of wavelength 1.8 A is (\[R=1.1\times {{10}^{-7}}{{m}^{-1}},b=1\] and \[\sqrt{5/33}=0.39\])
A.	Co, Z=27
B.	Iron, Z=26
C.	Mn, Z=25
D.	Ni, Z=28
Answer» B. Iron, Z=26

Discussion

3057.	An \[\alpha \] particle passes rapidly through the exact center of a hydrogen molecule, moving on a line perpendicular to the inter nuclear axis. The distance between the nuclei is b. Where on its path does the \[\alpha \] particle experience the greatest force? (Assume that the nuclei do not move much during the passage of the \[\alpha \] particle. Also neglect the electric field of the electrons in the molecule.)
A.	\[\frac{b}{2}\]
B.	\[\frac{b}{2\sqrt{2}}\]
C.	\[\frac{b}{\sqrt{2}}\]
D.	None of these
Answer» B. \[\frac{b}{2\sqrt{2}}\]

Discussion

3058.	A hydrogen atom in its ground state absorbs 10.2 eV of energy The orbital angular momentum is increased by
A.	\[1.05\times {{10}^{-34}}J-s\]
B.	\[3.16\times {{10}^{-34}}J-s\] [b] \[{{E}_{p}}=\frac{2{{K}_{ex}}}{{{\left( {{x}^{2}}+\frac{{{b}^{2}}}{4} \right)}^{3/2}}}\] For maximum \[{{E}_{p}}\] \[\frac{d{{E}_{p}}}{dx}=0\] \[\Rightarrow x=\frac{b}{2\sqrt{2}}\]
C.	\[2.11\times {{10}^{-34}}J-s\]
D.	\[4.22\times {{10}^{-34}}J-s\]
Answer» B. \[3.16\times {{10}^{-34}}J-s\] [b] \[{{E}_{p}}=\frac{2{{K}_{ex}}}{{{\left( {{x}^{2}}+\frac{{{b}^{2}}}{4} \right)}^{3/2}}}\] For maximum \[{{E}_{p}}\] \[\frac{d{{E}_{p}}}{dx}=0\] \[\Rightarrow x=\frac{b}{2\sqrt{2}}\]

Discussion

3059.	The wavelength of \[{{K}_{a}}\] X-rays produced by an X-ray tube is 0.76 A. Find the atomic number of the anode material of the tube?
A.	40
B.	30
C.	20
D.	10
Answer» B. 30

Discussion

3060.	An energy of 24.6 eV is required to remove one of the electrons from a neutral helium atom. The energy (in eV) required to remove both the electrons from a neutral helium atom is
A.	38.2
B.	49.2
C.	51.8
D.	79.0
Answer» E.

Discussion

3061.	The de-Broglie wavelength associated with the electron in the \[\,n=4\] level is :
A.	\[\frac{1}{4}th\] of the de-Broglie wavelength of the electron in the ground state.
B.	four times the de-Broglie wavelength of the electron in the ground state
C.	two times the de-Broglie wavelength of the electron in the ground state
D.	half of the de-Broglie wavelength of the electron in the ground state.
Answer» C. two times the de-Broglie wavelength of the electron in the ground state

Discussion

3062.	Electrons in a certain energy level \[n={{n}_{1}}\], can emit 3 spectral lines. When they are in another energy level, \[n={{n}_{2}}\]. They can emit 6 spectral lines. The orbital speed of the electrons in the two orbits are in the ratio of
A.	4 : 3
B.	3 : 4
C.	2 : 1
D.	1 : 2
Answer» B. 3 : 4

Discussion

3063.	A hydrogen atom in state n=6 makes two successive transitions and reaches the ground state. In the first transition a photon of 1.13 eV is emitted. Find the energy of the photon emitted in the second transition and the value of n in the intermediate state.
A.	12.1eV, n=3
B.	6.1eV, n=4
C.	2.1eV, n=3
D.	1.1eV, n=5.
Answer» B. 6.1eV, n=4

Discussion

3064.	Consider 3rd orbit of \[H{{e}^{+}}\](Helium), using non-relativistic approach, the speed of electron in this orbit will be [given \[K=9\times {{10}^{9}}\]constant and h (Plank's Constant) \[6.6\times {{10}^{-34}}Js\]]
A.	\[1.46\times {{10}^{6}}m/s\]
B.	\[0.73\times {{10}^{6}}m/s\]
C.	\[3.0\times {{10}^{8}}m/s\]
D.	\[2.92\times {{10}^{6}}m/s\]
Answer» B. \[0.73\times {{10}^{6}}m/s\]

Discussion

3065.	If a proton had a radius R and the charge was uniformly distributed, calculate using Bohr theory, the total ground state energy of a H-atom when R=0.1A.
A.	-13.6 eV
B.	-5.6 eV
C.	-3.67 eV
D.	-2.67 eV.
Answer» B. -5.6 eV

Discussion

3066.	The energy difference between the first two levels of hydrogen atom is 10.2 eV for another element of atomic number 10 and mass number 20, this will be
A.	2040 eV
B.	0.201 eV
C.	510 eV
D.	1020 eV
Answer» E.

Discussion

3067.	In a Rutherford experiment, the number of particles scattered at \[90{}^\circ \]angle are 28 per minute then number of scattered particles at an angle \[~60{}^\circ \] and \[120{}^\circ \] will be
A.	117 per minute, 25 per minute
B.	50 per minute, 12.5 per minute
C.	100 per minute, 200 per minute
D.	112 per minute, 12.4 per minute
Answer» E.

Discussion

3068.	A neutron travelling with a velocity v and kinetic energy E has a perfectly elastic head-on collision with a nucleus of an atom of mass number A at rest. The fraction of total energy retained by the neutron is approximately
A.	\[{{\left[ \left( A-1 \right)\left( A+1 \right) \right]}^{2}}\]
B.	\[{{\left[ \left( A+1 \right)\left( A-1 \right) \right]}^{2}}\]
C.	\[{{\left[ \left( A-1 \right)/A \right]}^{2}}\]
D.	\[{{\left[ \left( A+1 \right)/A \right]}^{2}}\]
Answer» B. \[{{\left[ \left( A+1 \right)\left( A-1 \right) \right]}^{2}}\]

Discussion

3069.	If the angular momentum of an electron in an orbit is J then the K.E. of the electron in that orbit is
A.	\[\,\frac{{{J}^{2}}}{2m{{r}^{2}}}\]
B.	\[\,\frac{Jv}{r}\]
C.	\[\,\frac{{{J}^{2}}}{2m}\]
D.	\[\,\frac{{{J}^{2}}}{2\pi }\]
Answer» B. \[\,\frac{Jv}{r}\]

Discussion

3070.	An electron in a hydrogen atom makes a transition from \[n={{n}_{1}}\] to\[n={{n}_{2}}\]. The time period of electron in the initial state is eight times that in the final state. Then which of the following statement is true?
A.	\[{{n}_{1}}=3{{n}_{2}}\]
B.	\[{{n}_{1}}=4{{n}_{2}}\]
C.	\[{{n}_{1}}=2{{n}_{2}}\]
D.	\[{{n}_{1}}=5{{n}_{2}}\]
Answer» D. \[{{n}_{1}}=5{{n}_{2}}\]

Discussion

3071.	If in hydrogen atom, radius of nth Bohr orbit is \[{{r}_{n}}\], frequency of revolution of electron in \[{{n}^{th}}\] orbit is \[{{f}_{n}}\], choose the correct option.
A.
B.
C.
D.	Both and
Answer» E.

Discussion

3072.	Assume in specific conditions only those transitions are allowed to hydrogen atoms in which the principal quantum number n changes by 2. Find the smallest wavelength emitted by hydrogen and wavelength emitted by hydrogen in the visible range (380 nm to 780 nm). respectively (in nm)
A.	103, 487
B.	123, 532
C.	211, 410
D.	320, 435
Answer» B. 123, 532

Discussion

3073.	Find the maximum angular speed \[(in\,\times {{10}^{16}}\,inrad/sec)\] of the electron of a hydrogen atom in a stationary orbit.
A.	2.1
B.	4.1
C.	8.5
D.	11.6
Answer» C. 8.5

Discussion

3074.	Which of the following statements are true regarding Bohr's model of hydrogen atom? (I) Orbiting speed of electron decreases as it shifts to discrete orbits away from the nucleus (II) Radii of allowed orbits of electron are proportional to the principal quantum number (III) Frequency with which electrons orbit around the nucleus in discrete orbits is inversely proportional to the cube of principal quantum number (IV) Binding force with which the electron is bound to the nucleus increases as it shifts o outer orbits Select correct answer using the codes given below. Codes:
A.	I and II
B.	II and IV
C.	I, II and III
D.	II, III and IV
Answer» B. II and IV

Discussion

3075.	Suppose that a material emits X-rays of wavelengths\[\,\lambda {{\kappa }_{\alpha }},\lambda {{\kappa }_{\beta }},{{\lambda }_{{{L}_{\alpha }}}}\], when it is excited by fast moving electrons; the wavelengths corresponding to \[{{K}_{\alpha }},{{K}_{\beta }},{{L}_{\alpha }}\]X- rays of the material respectively. Then we can write
A.	\[\,\lambda {{\kappa }_{\beta }}=\lambda {{\kappa }_{\alpha }}+{{\lambda }_{{{L}_{\alpha }}}}\]
B.	\[\sqrt{\,\lambda {{\kappa }_{\beta }}}=\sqrt{\lambda {{\kappa }_{\alpha }}}+\sqrt{{{\lambda }_{{{L}_{\alpha }}}}}\]
C.	\[\,\frac{1}{\lambda {{\kappa }_{\beta }}}=\frac{1}{\lambda {{\kappa }_{\alpha }}}+\frac{1}{{{\lambda }_{{{L}_{\alpha }}}}}\]
D.	\[\,\frac{1}{\sqrt{\lambda {{\kappa }_{\beta }}}}=\frac{1}{\sqrt{\lambda {{\kappa }_{\alpha }}}}+\frac{1}{\sqrt{{{\lambda }_{{{L}_{\alpha }}}}}}\]
Answer» D. \[\,\frac{1}{\sqrt{\lambda {{\kappa }_{\beta }}}}=\frac{1}{\sqrt{\lambda {{\kappa }_{\alpha }}}}+\frac{1}{\sqrt{{{\lambda }_{{{L}_{\alpha }}}}}}\]

Discussion

3076.	In the hydrogen atom, an electron makes a transition from n = 2 to n = 1. The magnetic field produced by the circulating electron at the nucleus -
A.	decreases 16 times
B.	increases 4 times
C.	decreases 4 times
D.	increases 32 times
Answer» E.

Discussion

3077.	In a hydrogen atom following the Bohr's postulates the product of linear momentum and angular momentum is proportional to \[{{(n)}^{x}}\] where 'n' is the orbit number. Then 'x' is-
A.	0
B.	2
C.	-2
D.	1
Answer» B. 2

Discussion

3078.	A hydrogen atom makes a transition from n=2 to n=1 and emits a photon. This photon strikes a doubly ionized lithium atom (z = 3) in excited state and completely removes the orbiting electron. The least quantum number for the excited state of the ion for the process is :
A.	2
B.	4
C.	5
D.	3
Answer» C. 5

Discussion

3079.	An \[\alpha \]-particle of energy 5 MeV is scattered through \[180{}^\circ \] by a fixed uranium nucleus. The distance of closest approach is of the order of
A.	\[{{10}^{-12}}cm\]
B.	\[{{10}^{-10}}cm\]
C.	\[{{10}^{-14}}cm\]
D.	\[{{10}^{-15}}cm\,\]
Answer» B. \[{{10}^{-10}}cm\]

Discussion

3080.	The momentum of hydrogen atom when a photon is emitted in a transition from \[{{n}_{i}}=10\]to \[{{n}_{f}}\] is-
A.	\[\,7\times {{10}^{-27}}\text{ }kg/ms~\]
B.	\[\,7\times {{10}^{27}}\text{ }kg/ms~\]
C.	\[\,3.5\times {{10}^{-27}}\text{ }kg/ms~\]
D.	\[\,3.5\times {{10}^{27}}\text{ }kg/ms~\]
Answer» B. \[\,7\times {{10}^{27}}\text{ }kg/ms~\]

Discussion

3081.	The wavelength \[{{K}_{\alpha }}\] of X-rays for two metals 'A' and ?B? are \[\frac{4}{1875R}\] and \[\frac{1}{675R}\] respectively, where 'R' is Rydberg constant. Find the number of elements lying between A and B according to their atomic numbers
A.	3
B.	1
C.	4
D.	5
Answer» D. 5

Discussion

3082.	Ionization energy of a hydrogen-like ion A is greater than that of another hydrogen-like ion B. If r, u, E and L represent the radius of the orbit, speed of the electron, energy of the atom and orbital angular momentum of the electron respectively then in ground state
A.	\[{{r}_{A}}>{{r}_{B}}\]
B.	\[{{u}_{A}}>{{u}_{B}}\]
C.	\[{{E}_{A}}>E{{ }_{B}}\]
D.	\[{{L}_{A}}<{{L}_{B}}\]
Answer» C. \[{{E}_{A}}>E{{ }_{B}}\]

Discussion

3083.	According to Bohr's theory, the time averaged magnetic field at the center (i.e. nucleus) of a hydrogen atom due to the motion of electrons in the nth orbit is proportional to : (n = principal quantum number)
A.	\[{{n}^{-4}}\]
B.	\[{{n}^{-5}}\]
C.	\[{{n}^{-3}}\]
D.	\[{{n}^{-2}}\]
Answer» E.

Discussion

3084.	As per Bohr model, the minimum energy (in eV) required to remove an electron from the ground state of doubly ionized Li atom (Z=3) is
A.	1.51
B.	13.6
C.	40.8
D.	122.4
Answer» E.

Discussion

3085.	A hydrogen atom and a doubly ionized lithium atom are both in the second excited state. If \[{{L}_{H}}\] and \[{{L}_{Li}}\] respectively represent their electronic angular momenta and \[{{E}_{H}}\] and \[{{E}_{Li}}\] their energies, then
A.	\[{{L}_{H}}>{{L}_{Li}}\text{ and }\|{{E}_{H}}\|\,>\,\|{{E}_{Li}}\|\]
B.	\[{{L}_{H}}={{L}_{Li}}\text{ and }\|{{E}_{H}}\|\,<\,\|{{E}_{Li}}\|\]
C.	\[{{L}_{H}}={{L}_{Li}}\text{ and }\|{{E}_{H}}\|\,>\,\|{{E}_{Li}}\|\]
D.	\[\alpha \]
Answer» C. \[{{L}_{H}}={{L}_{Li}}\text{ and }\|{{E}_{H}}\|\,>\,\|{{E}_{Li}}\|\]

Discussion

3086.	In the Bohr model of a hydrogen atom, the centripetal force is furnished by the coulomb attraction between the proton and the electron. If \[{{a}_{0}}\] is the radius of the ground state orbit, m is he mass, e is the charge on the electron and \[{{\varepsilon }_{0}}\] is the vacuum permittivity, the speed of the electron is
A.	0
B.	\[\frac{e}{\sqrt{{{\varepsilon }_{0}}a{{ }_{0}}m}}\]
C.	\[\frac{e}{\sqrt{4\pi {{\varepsilon }_{0}}a{{ }_{0}}m}}\]
D.	\[\frac{\sqrt{4\pi {{\varepsilon }_{0}}a{{ }_{0}}m}}{e}\]
Answer» D. \[\frac{\sqrt{4\pi {{\varepsilon }_{0}}a{{ }_{0}}m}}{e}\]

Discussion

3087.	In the Bohr's model of hydrogen-like atom the force between the nucleus and the electron is modified as \[F=\frac{{{e}^{2}}}{4\pi {{\varepsilon }_{0}}}\left( \frac{1}{{{r}^{2}}}+\frac{\beta }{{{r}^{3}}} \right),\] where \[\beta \] is a constant. For this atom, the radius of the nth orbit in terms of the Bohr radius \[\left( {{a}_{0}}=\frac{{{\varepsilon }_{0}}{{h}^{2}}}{m\pi {{e}^{2}}} \right)\] is:
A.	\[{{r}_{n}}={{a}_{0}}n-\beta \]
B.	\[{{r}_{n}}={{a}_{0}}{{n}^{2}}+\beta \]
C.	\[{{r}_{n}}={{a}_{0}}{{n}^{2}}-\beta \]
D.	\[{{r}_{n}}={{a}_{0}}n+\beta \]
Answer» D. \[{{r}_{n}}={{a}_{0}}n+\beta \]

Discussion

3088.	Consider the spectral line resulting from the transition \[n=2\to n=1\] in the atoms and ions given below. The shortest wavelength is produced by
A.	Hydrogen atom
B.	Deuterium atom
C.	Singly ionized Helium
D.	Doubly ionized Lithium
Answer» E.

Discussion

3089.	If elements with principal quantum number n>4 were not allowed in nature, the number of possible elements would be
A.	60
B.	32
C.	4
D.	64
Answer» B. 32

Discussion

3090.	If radiation corresponding to first line of "Balmer series" of \[H{{e}^{+}}\] ion knocked out electron from 1st excited state of H atom, the kinetic energy of ejected electron from H atom would be (eV) - [Given \[{{E}_{n}}=-\frac{{{Z}^{2}}}{{{n}^{2}}}\left( 13.6eV \right)\]]
A.	4.155 eV
B.	8.310 eV
C.	2.515 eV
D.	5.550 eV
Answer» B. 8.310 eV

Discussion

3091.	An excited state of doubly ionized Lithium \[(L{{i}^{2+}})\] has an orbital radius that is about 1.33 times that of the ground state of hydrogen (H) (in Bohr's theory). The ratio of energy of the two states, \[E(L{{i}^{2+}})/E(H)\] is
A.	2.25
B.	4.5
C.	1
D.	9
Answer» B. 4.5

Discussion

3092.	The energy of \[H{{e}^{+}}\] in the ground state is -54.4 eV, then the energy of \[L{{i}^{++}}\] in the first excited state will be
A.	-30.6 eV
B.	27.2 eV
C.	-13.6 eV
D.	- 27.2 eV
Answer» B. 27.2 eV

Discussion

3093.	A 220 volts input is supplied to a transformer. The output circuit draws a current of 2.0 ampere at 440 volts. If the efficiency of the transformer is 80%, the current drawn by the primary windings of the transformer is
A.	3.6 ampere
B.	2.8 ampere
C.	2.5 ampere
D.	5.0 ampere
Answer» E.

Discussion

3094.	A transistor-oscillator using a resonant circuit with an inductor L (of negligible resistance) and a capacitor C in series produce oscillations of frequency f. If L is doubled and C is changed to 4C, the frequency will be
A.	\[8f\]
B.	\[f/2\sqrt{2}\]
C.	\[f/2\]
D.	\[f/4\]
Answer» C. \[f/2\]

Discussion

3095.	The tuning circuit of a radio receiver has a resistance of \[50\,\Omega \], an inductor of 10 mH and a variable capacitor. A 1 MHz radio wave produces a potential difference of 0.1 mV. The values of the capacitor to produce resonance is \[(Take\,{{\pi }^{2}}=10)\]
A.	2.5 pF
B.	5.0 pF
C.	25 pF
D.	50 pF
Answer» B. 5.0 pF

Discussion

3096.	A step up transformer operates on a 230 V line and supplies a current of 2 ampere. The ratio of primary and secondary winding is 1:25. The current in primary is
A.	25 A
B.	50 A
C.	15 A
D.	12.5 A
Answer» C. 15 A

Discussion

3097.	A transformer rated at 10 KW is used to connect a 5 KV transmission line to a 240V circuit. The ratio of turns in the windings of the transformer is:
A.	5
B.	20.8
C.	104
D.	40
Answer» C. 104

Discussion

3098.	In a series LCR circuit, the difference of the frequencies at which current amplitude falls to\[\frac{1}{\sqrt{2}}\] of the current amplitude at resonance is
A.	\[\frac{R}{2\pi L}\]
B.	\[\frac{R}{\pi L}\]
C.	\[\frac{2R}{\pi L}\]
D.	\[\frac{3R}{2\pi L}\]
Answer» B. \[\frac{R}{\pi L}\]

Discussion

3099.	A capacitor in an LC oscillator has a maximum potential difference of 17 V and a maximum energy of \[160\,\mu J\]. When the capacitor has a potential difference of 5V and an energy of \[10\,\mu J,\] what is the energy stored in the magnetic field?
A.	\[10\,\mu J\]
B.	\[150\,\mu J\]
C.	\[160\,\mu J\]
D.	\[170\,\mu J\]
Answer» C. \[160\,\mu J\]

Discussion

3100.	For long distance transmission, the A.C.is stepped up because of high voltage, the transmission is
A.	faster
B.	economical
C.	undamped
D.	less dangerous
Answer» D. less dangerous

Discussion

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

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

If the atom \[_{100}F{{m}^{257}}\] follows the Bohr model and the radius of \[_{100}F{{m}^{257}}\] is n times the Bohr radius, then find n.

In Rutherford scattering experiment, what will be the correct angle for a-scattering for an impact parameter, b=0?

Electrons are bombarded to excite hydrogen atoms and six spectral lines are observed. If \[{{E}_{g}}\] is the ground state energy of hydrogen, the minimum energy the bombarding electrons should posses is

In the Rutherford experiment, a-particles are scattered from a nucleus as shown. Out of the four paths, which path is not possible?

The element which has a \[{{K}_{\alpha }}\] x-rays line of wavelength 1.8 A is (\[R=1.1\times {{10}^{-7}}{{m}^{-1}},b=1\] and \[\sqrt{5/33}=0.39\])

A hydrogen atom in its ground state absorbs 10.2 eV of energy The orbital angular momentum is increased by

The wavelength of \[{{K}_{a}}\] X-rays produced by an X-ray tube is 0.76 A. Find the atomic number of the anode material of the tube?

An energy of 24.6 eV is required to remove one of the electrons from a neutral helium atom. The energy (in eV) required to remove both the electrons from a neutral helium atom is

The de-Broglie wavelength associated with the electron in the \[\,n=4\] level is :

Electrons in a certain energy level \[n={{n}_{1}}\], can emit 3 spectral lines. When they are in another energy level, \[n={{n}_{2}}\]. They can emit 6 spectral lines. The orbital speed of the electrons in the two orbits are in the ratio of

A hydrogen atom in state n=6 makes two successive transitions and reaches the ground state. In the first transition a photon of 1.13 eV is emitted. Find the energy of the photon emitted in the second transition and the value of n in the intermediate state.

Consider 3rd orbit of \[H{{e}^{+}}\](Helium), using non-relativistic approach, the speed of electron in this orbit will be [given \[K=9\times {{10}^{9}}\]constant and h (Plank's Constant) \[6.6\times {{10}^{-34}}Js\]]

If a proton had a radius R and the charge was uniformly distributed, calculate using Bohr theory, the total ground state energy of a H-atom when R=0.1A.

The energy difference between the first two levels of hydrogen atom is 10.2 eV for another element of atomic number 10 and mass number 20, this will be

In a Rutherford experiment, the number of particles scattered at \[90{}^\circ \]angle are 28 per minute then number of scattered particles at an angle \[~60{}^\circ \] and \[120{}^\circ \] will be

A neutron travelling with a velocity v and kinetic energy E has a perfectly elastic head-on collision with a nucleus of an atom of mass number A at rest. The fraction of total energy retained by the neutron is approximately

If the angular momentum of an electron in an orbit is J then the K.E. of the electron in that orbit is

An electron in a hydrogen atom makes a transition from \[n={{n}_{1}}\] to\[n={{n}_{2}}\]. The time period of electron in the initial state is eight times that in the final state. Then which of the following statement is true?

If in hydrogen atom, radius of nth Bohr orbit is \[{{r}_{n}}\], frequency of revolution of electron in \[{{n}^{th}}\] orbit is \[{{f}_{n}}\], choose the correct option.

Assume in specific conditions only those transitions are allowed to hydrogen atoms in which the principal quantum number n changes by 2. Find the smallest wavelength emitted by hydrogen and wavelength emitted by hydrogen in the visible range (380 nm to 780 nm). respectively (in nm)

Find the maximum angular speed \[(in\,\times {{10}^{16}}\,inrad/sec)\] of the electron of a hydrogen atom in a stationary orbit.

In the hydrogen atom, an electron makes a transition from n = 2 to n = 1. The magnetic field produced by the circulating electron at the nucleus -

In a hydrogen atom following the Bohr's postulates the product of linear momentum and angular momentum is proportional to \[{{(n)}^{x}}\] where 'n' is the orbit number. Then 'x' is-

A hydrogen atom makes a transition from n=2 to n=1 and emits a photon. This photon strikes a doubly ionized lithium atom (z = 3) in excited state and completely removes the orbiting electron. The least quantum number for the excited state of the ion for the process is :

An \[\alpha \]-particle of energy 5 MeV is scattered through \[180{}^\circ \] by a fixed uranium nucleus. The distance of closest approach is of the order of

The momentum of hydrogen atom when a photon is emitted in a transition from \[{{n}_{i}}=10\]to \[{{n}_{f}}\] is-

The wavelength \[{{K}_{\alpha }}\] of X-rays for two metals 'A' and ?B? are \[\frac{4}{1875R}\] and \[\frac{1}{675R}\] respectively, where 'R' is Rydberg constant. Find the number of elements lying between A and B according to their atomic numbers

Ionization energy of a hydrogen-like ion A is greater than that of another hydrogen-like ion B. If r, u, E and L represent the radius of the orbit, speed of the electron, energy of the atom and orbital angular momentum of the electron respectively then in ground state

According to Bohr's theory, the time averaged magnetic field at the center (i.e. nucleus) of a hydrogen atom due to the motion of electrons in the nth orbit is proportional to : (n = principal quantum number)

As per Bohr model, the minimum energy (in eV) required to remove an electron from the ground state of doubly ionized Li atom (Z=3) is

A hydrogen atom and a doubly ionized lithium atom are both in the second excited state. If \[{{L}_{H}}\] and \[{{L}_{Li}}\] respectively represent their electronic angular momenta and \[{{E}_{H}}\] and \[{{E}_{Li}}\] their energies, then

Consider the spectral line resulting from the transition \[n=2\to n=1\] in the atoms and ions given below. The shortest wavelength is produced by

If elements with principal quantum number n>4 were not allowed in nature, the number of possible elements would be

If radiation corresponding to first line of "Balmer series" of \[H{{e}^{+}}\] ion knocked out electron from 1st excited state of H atom, the kinetic energy of ejected electron from H atom would be (eV) - [Given \[{{E}_{n}}=-\frac{{{Z}^{2}}}{{{n}^{2}}}\left( 13.6eV \right)\]]

An excited state of doubly ionized Lithium \[(L{{i}^{2+}})\] has an orbital radius that is about 1.33 times that of the ground state of hydrogen (H) (in Bohr's theory). The ratio of energy of the two states, \[E(L{{i}^{2+}})/E(H)\] is

The energy of \[H{{e}^{+}}\] in the ground state is -54.4 eV, then the energy of \[L{{i}^{++}}\] in the first excited state will be

A 220 volts input is supplied to a transformer. The output circuit draws a current of 2.0 ampere at 440 volts. If the efficiency of the transformer is 80%, the current drawn by the primary windings of the transformer is

A transistor-oscillator using a resonant circuit with an inductor L (of negligible resistance) and a capacitor C in series produce oscillations of frequency f. If L is doubled and C is changed to 4C, the frequency will be

The tuning circuit of a radio receiver has a resistance of \[50\,\Omega \], an inductor of 10 mH and a variable capacitor. A 1 MHz radio wave produces a potential difference of 0.1 mV. The values of the capacitor to produce resonance is \[(Take\,{{\pi }^{2}}=10)\]

A step up transformer operates on a 230 V line and supplies a current of 2 ampere. The ratio of primary and secondary winding is 1:25. The current in primary is

A transformer rated at 10 KW is used to connect a 5 KV transmission line to a 240V circuit. The ratio of turns in the windings of the transformer is:

In a series LCR circuit, the difference of the frequencies at which current amplitude falls to\[\frac{1}{\sqrt{2}}\] of the current amplitude at resonance is

A capacitor in an LC oscillator has a maximum potential difference of 17 V and a maximum energy of \[160\,\mu J\]. When the capacitor has a potential difference of 5V and an energy of \[10\,\mu J,\] what is the energy stored in the magnetic field?

For long distance transmission, the A.C.is stepped up because of high voltage, the transmission is