JEE Main Physics - Atoms Molecules and Nuclei
Exam Duration: 60 Mins Total Questions : 30
Choose CORRECT statement
- (a)
Rutherford's scattering experiment proves the existence of positively charged nucleus
- (b)
The trijectory of a scattered alpha-particle is a hyperpola
- (c)
According to Maxwell's classical theory of electro-magnetic theory, the Rutherford model of atom is unstable
- (d)
ALL OF THE ABOVE
Choose INCORRECT statement :
- (a)
The nuclear atomic model was first proposed by J.J Thomson
- (b)
The nuclear atomic model was first proposed by E.Rutherford
- (c)
The shape of electron orbits proposed by Rutherford is circular
- (d)
According to classical theory the proposed circular path of an electron in Rutherford atom will be spiral
Rutherford's alpha-particle scattering experiment gave experimental information about
- (a)
the charge on alpha-particle
- (b)
the size of atom
- (c)
the size of nucleus
- (d)
the force between alpha-particle and proton in the nucleus
The speed of an electron in the orbit of hydrogen atom in the ground state is [C = speed of light ]
- (a)
C
- (b)
\(\frac { C }{ 10 } \)
- (c)
\(\frac { C }{ 2 } \)
- (d)
\(\frac { C }{ 137 } \)
The ground state energy of H-atom is 13.6 eV. The energy needed to ionise H-atom from its second excited state is
- (a)
1.51 eV
- (b)
3.4 eV
- (c)
13.6 eV
- (d)
12.1 eV
The order of energies of energy levels A, B and C is \({ E }_{ A }<{ E }_{ B }<{ E }_{ C }\). If the wavelength corresponding to transitions \(C\longrightarrow B,\quad B\longrightarrow A\quad and\quad C\longrightarrow A\quad are\quad { \lambda }_{ 1 },\quad { \lambda }_{ 2 }\quad and\quad { \lambda }_{ 3 }\) respectively, then which of the following relations is correct?
- (a)
\({ \lambda }_{ 1 }+{ \lambda }_{ 2 }+{ \lambda }_{ 3 }=0\)
- (b)
\({ \lambda }_{ 3 }^{ 2 }={ \lambda }_{ 1 }^{ 2 }+{ \lambda }_{ 2 }^{ 2 }\)
- (c)
\({ \lambda }_{ 3 }={ \lambda }_{ 1 }+{ \lambda }_{ 2 }\)
- (d)
\({ \lambda }_{ 3 }=\frac { { \lambda }_{ 1 }{ \lambda }_{ 2 } }{ { \lambda }_{ 1 }+{ \lambda }_{ 2 } } \)
If mass of electron is reduced to half, the Rydberg constant
- (a)
remains unchanged
- (b)
becomes half
- (c)
becomes double
- (d)
becomes one fourth
The observations of a faint line very near to blue line of the hydrogen spectrum led to the discovery of
- (a)
ghost lines
- (b)
dueterium
- (c)
positron
- (d)
NONE OF THE ABOVE
The Lyman transitions invlove
- (a)
largest changes of energy
- (b)
smallest changes of energy
- (c)
largest changes of potential energy
- (d)
smallest changes of energy
The volume of a nucleus is smaller than that of the atom by a factor of about
- (a)
10
- (b)
1010
- (c)
1015
- (d)
1012
The mass number of a nucleus is
- (a)
always less than its atomic number
- (b)
always more than its atomic number
- (c)
sometimes equal to its atomic number
- (d)
sometimes more than and sometimes equal to its atomic number
The decay constant of \(_{ 80 }{ Po }^{ 206 }\) is \(\lambda \). Its half life and mean life respectively are
- (a)
\(\frac { 1 }{ \lambda } and\quad \frac { { log }_{ e }\quad 2 }{ \lambda } \)
- (b)
\(\frac { { log }_{ e }\quad 2 }{ \lambda } and\quad \frac { 1 }{ \lambda } \)
- (c)
\({ log }_{ e }\quad 2\quad and\quad \frac { 1 }{ \lambda } \)
- (d)
\(\frac { 1 }{ \lambda } \quad and\quad \lambda { log }_{ e }\quad 2\)
A nucleus \(_{ Z }{ X }^{ A }\) emits an \(\alpha \)-particle. The resultant nucleus emits a \({ \beta }^{ + }\)particle. The respective atomic and mass numbers of the final nucleus will be
- (a)
Z - 3, A - 4
- (b)
Z - 1, A - 4
- (c)
Z - 2, A - 4
- (d)
Z, A - 2
If N1 = N0 \({ e }^{ -\lambda { t }_{ 1 } }\), then the number of atoms decayed during time interval from t1 and t2 (t2>t1) will be
- (a)
\({ N }_{ { t }_{ 1 } }-{ N }_{ { t }_{ 2 } }={ N }_{ 0 }[????{ e }^{ -\lambda { t }_{ 1 } }-{ e }^{ -\lambda { t }_{ 2 } }]\)
- (b)
\({ N }_{ { t }_{ 2 } }-{ N }_{ { t }_{ 1 } }={ N }_{ 0 }[{ e }^{ -\lambda { t }_{ 2 } }-{ e }^{ -\lambda { t }_{ 1 } }]\)
- (c)
\({ N }_{ { t }_{ 2 } }-{ N }_{ { t }_{ 1 } }={ N }_{ 0 }[{ e }^{ \lambda { t }_{ 2 } }-{ e }^{ -\lambda { t }_{ 1 } }]\)
- (d)
NONE OF THE ABOVE
Complete the equation for the following fission process :
\({ _{ 92 }U }^{ 235 }+{ _{ 0 }n }^{ 1 }\longrightarrow ...+{ _{ 38 }Kr }^{ 90 }+...\)
- (a)
\({ _{ 54 }Xe }^{ 143 }+3{ _{ 0 }n }^{ 1 }\)
- (b)
\({ _{ 54 }Xe }^{ 145 }\)
- (c)
\({ _{ 57 }Xe }^{ 142 }\)
- (d)
\({ _{ 54 }Xe }^{ 142 }+{ _{ 0 }n }^{ 1 }\)
In the nuclear reaction \({ _{ 6 }C }^{ 11 }\longrightarrow _{ 5 }{ B }^{ 11 }+{ \beta }^{ + }+X,\) what does X stand for?
- (a)
An electron
- (b)
A photon
- (c)
Anti-neutrino
- (d)
A neutrino
Percentage of the original number of atoms in a radioactive sample remaining at the end of one mean life is
- (a)
63
- (b)
37
- (c)
50
- (d)
60
The energy released in nuclear fission mostly appears as
- (a)
heat
- (b)
kinetic energy of fission fragments
- (c)
radio-active radiations
- (d)
chemical energy
In the process of fission, the binding energy per nucleon
- (a)
decreases
- (b)
increases
- (c)
remains unchanged
- (d)
is more for mass number A<56 but is less for A>56
A radioactive nucleus can decay by two different processes. The mean value of period for first process is t1 and that for the second process is t2. The effective mean period for two processes is
- (a)
\(1/2({ t }_{ 1 }+{ t }_{ 2 })\)
- (b)
\(({ t }_{ 1 }+{ t }_{ 2 })\)
- (c)
\(\sqrt { { t }_{ 1 }{ .t }_{ 2 } } \)
- (d)
\(\frac { { t }_{ 1 }{ t }_{ 2 } }{ { t }_{ 1 }+{ t }_{ 2 } } \)
The binding energy per nucleon of O16 is 7.97 MeV and that of O17 is 7.75 MeV. The energy in MeV required to remove a neutron from O17 is
- (a)
3.52
- (b)
3.64
- (c)
4.23
- (d)
7.86
The half life of radio-active substance is 40 days. The substance will disintegrate completely in
- (a)
40 days
- (b)
400 days
- (c)
4000 days
- (d)
infinite
The average life of bound neutron in a nucleus is
- (a)
to absorb neutrons
- (b)
to cool the reactor
- (c)
to slow down the neutrons to thermal energies
- (d)
to control the energy released in the reactor
A gas with hydrogen like atoms absorbs a radiation of 68eV. Consequently, the atoms emit radiations of only 3 wavelengths. The final state of atom is
- (a)
n=1
- (b)
n=3
- (c)
n=2
- (d)
n=4
The electron in a hydrogen atom makes transition from shell M to shell L. The ratio of magnitudes of initial to final centripetal acceleration of the electron is
- (a)
9:4
- (b)
81:16
- (c)
4:9
- (d)
16:81
An electron in hydrogen atom after absorbing energy of photon jumps from energy state n1 and n2(n2>n1). Then it returns to ground state after emitting six different wavelengths in emission spectrum. The energy of emitted photons is either equal to, less than or greater than the absorbed photons. Then n1 and n2 are
- (a)
n1=4, n2=3
- (b)
n2=5, n1=3
- (c)
n2=4, n1=2
- (d)
n2=4, n1=1
In the hydrogen atom, the reference level of potential energy is assumed to be zero at the ground state level. Choose the correct statement
- (a)
the total energy of the shell increases with increase in the value of n.
- (b)
the total energy of the shell decrease with increase in the value of n
- (c)
the difference in total energy of any two shells remains the same
- (d)
the total energy at the ground state becomes 13.6eV
Hydrogen (1H1), Deuterium (1H2), singly ionised Helium (2He4)+ and doubly ionised lithium (2Li6)++ all have one electron around the nucleus. Consider an electron transition from n=2 to n=1. If the wavelengths of emitted radiation are \(\lambda_1,\lambda_2,\lambda_3 \ and \ \lambda_4\) respectively then approximately which one of the following is correct?
- (a)
\(\lambda_1=\lambda_2=4\lambda_3=\lambda_4\)
- (b)
\(\lambda_1=2\lambda_2=3\lambda_3=4\lambda_4\)
- (c)
\(4\lambda_1=2\lambda_2=2\lambda_3=\lambda_4\)
- (d)
\(\lambda_1=2\lambda_2=2\lambda_3=\lambda_4\)
In an H-atom, electron makes a transition from an energy level with quantum number n to quantum number (n-1). If n>>1, then frequency of emitted radiation is proportional to
- (a)
\(1\over n\)
- (b)
\(1\over n^2\)
- (c)
\(1\over n^{3/2}\)
- (d)
\(1\over n^3\)