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Recent questions in Class12
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JEEMAIN and NEET
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Physics
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Class12
Class12
Electric Charges and Fields
Electrostatic Potential and Capacitance
Current Electricity
Moving Charges and Magentism
Magnetism and Matter
Electromagnetic Induction
Alternating Current
Electromagnetic Waves
Ray Optics and Optical Instruments
Wave Optics
Dual Nature of Matter and Radiation
Atoms
Nucleii
Semiconductor Materials and Electronic Devices
Communication Systems
Experimental Skills in Physics
An electric line of force in the $xy$ plane is given by equation $x^2+y^2=1$. A particle with unit positive charge, initially at rest at the point $x = 1, y = 0$ in the $xy$ plane
jeemain
aipmt
physics
cbse
class12
ch1
electric-charges-and-fields
electric-field
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
If $c$ is the speed of electromagnetic waves in vacuum, their speed in a medium of dielectric constant $K$ and relative permeability $ \mu_r$ is
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q40
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
A beam of light travelling along $ x$ - axis is described by the electric field $E_y = (600 V/m) \sin \omega (t - x/c)$ then maximum magnetic force on a charge $q = 2e$, moving along $y$ - axis with a speed of $3.0 \times 10^7m/s$ is $(e = 1.6 \times 10^{-19} C)$
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q39
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
About 5% of the power of a $100\: W$ light bulb is converted to visible radiation. What is the average intensity of visible radiation at a distance of $10\: m$ from the bulb?
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q38
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
A parallel plate capacitor of area $50\: cm^2$ and plate separation $3\: mm$ is charged initially to $80\: \mu C$. Due to a radioactive source nearby, the medium between the plates gets slightly conducting and the plate loses charge initially at the rate of $1.5 \times 10^{-8}C/s$. What is the magnitude and direction of displacement current?
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
displacement-current
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
A parallel plate capacitor with plate area $A$ and separation $d$ between the plates is charged by a constant current $i$. Consider a plane surface of area $A/4$ parallel to the plates and drawn symmetrically between the plates. Calculate the displacement current through this area.
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
displacement-current
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
Find the energy of a photon in electron volt of microwaves having wavelength $3mm.(1\: eV = 1.6 \times 10^{-19}J)$
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q35
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
Light with an energy flux of $18\: W/cm^2$ surface has an area of $ 20\: cm^2$ falls on a non-reflecting surface at normal incidence. If the , the average force exerted on the surface during a $30$ minute time span is
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q34
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
The magnetic field in a plane electromagnetic wave is given by $B_y= 2 \times 10^{-7} \: \sin (0.5\times10^3x+1.5\times10^{11}t)T$ The wavelength and frequency of the wave are
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q33
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
A plane electromagnetic wave of frequency $25\: MHz$ travels in free space along the $x$ - direction. At a particular point in space and time, $E= 6.3 \: jV/m$. What is B at this point?
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
The intensity of the sunlight reaching the earth is $1380\; W/m^2$. Calculate the amplitude of the magnetic field in the light wave. Assume the light to be a plane monochromatic wave.
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q31
medium
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
The wavelength of a radio wave of frequency of $1\: MHz$ is:
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q30
easy
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
Which of the following are not electromagnetic waves?
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q29
easy
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
An isotope is radioactive . It is being produced at constant rate b . Half - life of radioactive substance is a . After some time no.of radioactive nuclei become constant . Then value of this constant is .
jeemain
physics
class12
atoms-and-nuclei
easy
asked
Feb 27, 2014
by
yamini.v
1
answer
A radioactive material of Lay life T was produced in a nuclear reactor at different instants , the quantity produced second time was twice of that produced first time . If now their present activities are $\;A_{1}\;$ and $\;A_{2}\;$ respectively . Then their age difference equals :
jeemain
physics
class12
atoms-and-nuclei
medium
asked
Feb 27, 2014
by
yamini.v
1
answer
The radii of two nuclei with atomic ratio of no .1 & 27 is ?
jeemain
physics
class12
atoms-and-nuclei
medium
asked
Feb 27, 2014
by
yamini.v
1
answer
Which of following are not deflected by a magnetic field ?
jeemain
physics
class12
atoms-and-nuclei
easy
asked
Feb 27, 2014
by
yamini.v
1
answer
A radioactive nucleus can decay by two different process . The half life for first process is $\;t_{1}\;$ and that for second process is $\;t_{2}\;$. Find the effective half life of nucleus
jeemain
physics
class11
ch13
nuclei
nuclear-physics
easy
radioactivity
half-life
alpha-beta-and-gamma-decay
medium
asked
Feb 27, 2014
by
yamini.v
1
answer
Mark the correct option
jeemain
aipmt
physics
cbse
class12
ch4
moving-charge-and-magnetism
amperes-circuital-law
easy
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
S1: Faraday’s Law of electromagnetic induction is induced emf, $e = \large\frac{-d \phi }{dt}$ \[\] S2: Due to changing magnetic field, if $E$ is induced electric field, then $e = \int E \: dl$ \[\] S3: From above two statements, $ \int E\: dl =\large\frac{-d \phi }{dt}$
jeemain
aipmt
physics
cbse
class12
ch6
electromagnetic-induction
faradays-law
easy
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
Relative permittivity and permeability of a material are $ \in_r$ and $ \mu_r$ , respectively. Which of the following values of these quantities are allowed for a diamagnetic material?
jeemain
aipmt
physics
cbse
class12
ch5
magnetism-and-matter
magnetic-properties-of-materials
easy
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
A neutron moving with speed V makes a head on collision with a hydrogen atom in ground state kept at a rest. Then find the minimum kinetic energy of neutron for which inelastic (completely of partially ) collision may take place . (mass of neutron =mass of hydrogen =$\;1.67\times10^{-27} Kg$) .
jeemain
physics
class12
atoms-and-nuclei
difficult
asked
Feb 27, 2014
by
yamini.v
1
answer
The nuclear reaction $\;n + _{5}^{10}B \to _{3}^{7}{Li}+_{2}^{4}He\;$ is observed to occur when very slow - moving neutrons $\;(M_{n}=1.0087 u)\;$ strike a boron atom at rest . For a particular reaction in which $\;K_{n} \approx 0\;,$ the helium $\;(M_{He}=4.0026 u)\;$ is observed to have a speed of $\;9.30\times 10^{6} m/s\;.$ Then the kinetic energy of $\;(lithium\;M_{li}=7.016 u)\;$. Find Q value of reaction .
jeemain
physics
class12
atoms-and-nuclei
medium
asked
Feb 27, 2014
by
yamini.v
1
answer
Some radio waves of frequency of about $1.5 \times 10^9\: Hz$ was received by a radio-telescope from distant star. If the speed of the waves is $3 \times 10^5\: km/s$ , then the wave- length of the wave will be:
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q25
easy
asked
Feb 27, 2014
by
thanvigandhi_1
1
answer
Electromagnetic waves are transverse in nature is evident by
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q24
easy
asked
Feb 27, 2014
by
thanvigandhi_1
2
answers
The nuclear reaction $\;n + _{5}^{10}B \to _{3}^{7}{Li}+_{2}^{4}He\;$ is observed to occur when very slow - moving neutrons $\;(M_{n}=1.0087 u)\;$ strike a boron atom at rest . For a particular reaction in which $\;K_{n} \approx 0\;,$ the helium $\;(M_{He}=4.0026 u)\;$ is observed to have a speed of $\;9.30\times 10^{6} m/s\;.$ Then the kinetic energy of $\;(lithium\;M_{li}=7.016 u)\;$
jeemain
physics
class12
atoms-and-nuclei
medium
asked
Feb 27, 2014
by
yamini.v
1
answer
In chain analysis of a rock , the mass ratio of two radioactive isotope is found to be $\;100 \%\;$ . The mean lives of two isotopes are $\;4 \times 10^{9}\;$years and $\;2\times10^{9}\;$years respectively . If it is assumed that at time of formation of rock , both isotopes were in equal proportion . Then calculate age of rock . Ratio of atomic weights of two isotope is $\;1.02 \%\;(log_{10}^{1.02}=0.0086)$
jeemain
physics
class12
atoms-and-nuclei
difficult
asked
Feb 27, 2014
by
yamini.v
1
answer
The mean lives of radioactive substance are 1620 year and 405 year for $\;\alpha\;$ emission and $\;\beta\;$ emission respectively . Find time during which $\;{\large\frac{3}{4}}^{th}\;$ of a sample will decay if it is decaying both by $\;\alpha\;$ emission and $\;\beta\;$ emission simultaneously .
jeemain
physics
class11
ch13
nuclei
nuclear-physics
radioactivity
alpha-beta-and-gamma-decay
difficult
asked
Feb 27, 2014
by
yamini.v
1
answer
The disintegration rate of a radioactive sample at a certain instant is 4750 dpm . Five minute later rate becomes 2700 disintegration per minute ; Then the half-life of sample is
jeemain
physics
class11
ch13
nuclei
nuclear-physics
medium
radioactivity
half-life
asked
Feb 27, 2014
by
yamini.v
1
answer
Infrared radiation is detected by
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q23
easy
asked
Feb 26, 2014
by
thanvigandhi_1
1
answer
The electromagnetic waves that stimulate blood circulation are
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q22
easy
asked
Feb 26, 2014
by
thanvigandhi_1
1
answer
The oscillating electric & magnetic vectors of an electromagnetic wave are oriented along
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
easy
asked
Feb 26, 2014
by
thanvigandhi_1
1
answer
$UHF$ range if electromagnetic waves can be propagated by means of
jeemain
aipmt
physics
cbse
class12
ch15
communication-systems
bandwidth-of-signals-and-transmission-medium
easy
asked
Feb 26, 2014
by
thanvigandhi_1
1
answer
Electromagnetic waves are produced by:
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q19
easy
asked
Feb 26, 2014
by
thanvigandhi_1
1
answer
The pressure exerted by an electromagnetic wave of intensity $I$ on a non-reflecting surface is ($c$ is velocity of light)
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q18
easy
asked
Feb 26, 2014
by
thanvigandhi_1
1
answer
The amplitude of the magnetic field part of a harmonic electromagnetic wave in vacuum is $B_o = 510\: nT$. What is the amplitude o the electric field part of the wave?
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q17
easy
asked
Feb 26, 2014
by
thanvigandhi_1
1
answer
The disintegration rate of a radioactive sample at a certain instant is 4750 dpm . Five minute later rate becomes 2700 disintegration per minute . Then the decay constant is
jeemain
physics
class11
ch13
nuclei
nuclear-physics
medium
radioactivity
decay-constant
asked
Feb 26, 2014
by
yamini.v
2
answers
Calculate wavelength of emitted characteristic X-ray from a tungsten (Z=74) target when an electron drops from an M shell to a vacancy in K shell
jeemain
physics
class12
atoms-and-nuclei
difficult
asked
Feb 26, 2014
by
yamini.v
1
answer
Consider a hypothitical hydrogen -like atom . The wavelength in A for spectrical lines for transitions from n=P to n=1 are given by $\;\lambda=\large\frac{1500P^2}{P^2-1}\;$ where P=2 , 3 ,4,----. Then wavelength of least energetic and most energetic photons in this series .
jeemain
physics
class12
atoms-and-nuclei
difficult
asked
Feb 26, 2014
by
yamini.v
1
answer
A particle of charge equal to that of an electron e , and mass 208 times the mass of electron (called $\;\mu-\;$ meson ) moves in a circular orbit around a nucleus of charge +3e . (Take the mass of nucleus to be infinite ) . Then radius of $n^{th}\;$ Bohr orbit is . Find wavelength of radiation emitted when $\;mu\;$- meson jumps from third orbit to first orbit
jeemain
physics
class12
atoms-and-nuclei
difficult
asked
Feb 26, 2014
by
yamini.v
1
answer
A particle of charge equal to that of an electron e , and mass 208 times the mass of electron (called $\;\mu-\;$ meson ) moves in a circular orbit around a nucleus of charge +3e . (Take the mass of nucleus to be infinite ) . Then radius of $n^{th}\;$ Bohr orbit is . Find the value of n for which radius of orbit is approximately the same as that of first Bohr orbit for hydrogen atom.
jeemain
physics
class12
atoms-and-nuclei
medium
asked
Feb 26, 2014
by
yamini.v
1
answer
A particle of charge equal to that of an electron e , and mass 208 times the mass of electron (called $\;\mu-\;$ meson ) moves in a circular orbit around a nucleus of charge +3e . (Take the mass of nucleus to be infinite ) . Then radius of $n^{th}\;$ Bohr orbit is
jeemain
physics
class12
atoms-and-nuclei
medium
asked
Feb 26, 2014
by
yamini.v
1
answer
A moving hydrogen atom makes a head-on in elastic collision with a stationary hydrogen atom. Before collision both atoms are in ground state and after collision they move together. What is minimum velocity of moving hydrogen atom ignore of atoms is to be given the minimum excitation energy after the collision ?
jeemain
physics
class12
atoms-and-nuclei
medium
asked
Feb 26, 2014
by
yamini.v
1
answer
A doubly ionized lithium atom is hydrogen like atomic number $Z=3$ . Find the wavelength of radiation required to excite electron in $\;Li^{+2}\;$ from first to third Bohr orbit . Given the ionization energy of hydrogen atom as $\;13.6 eV\;.\;$
jeemain
physics
class12
atoms-and-nuclei
difficult
asked
Feb 26, 2014
by
yamini.v
1
answer
In an ore containing uranium , the ratio of $\;U^{238}\;$ to $\;Pb^{206}\;$ nuclei is $3$ . Then calculate age of ore assuming that all lead present in ore is final stable products of $\;U^{238}\;$ . Take half life if $\;U^{238}\;$ to be $\;4.5 \times 10^{9}\;$years
jeemain
physics
class12
atoms-and-nuclei
medium
asked
Feb 26, 2014
by
yamini.v
1
answer
A tritium gas target is bombareled with a beam of mono-energetic protons of K.E 3MeV . What is K.E of neutrons emitted at an angle $\;30^{0}\;$ with incident beam ? \[\] Atomic masses are $\;H^{1}=1.007276 amu$ \[\] $\;m^{1}=1.008665 amu$\[\] $\;H_{1}^{3}=3.06056 amu$\[\] and $\;He^{2}=3.016030 amu$
jeemain
physics
class12
atoms-and-nuclei
difficult
asked
Feb 26, 2014
by
yamini.v
1
answer
A small quantity of solution containing $\;Na^{24}\;$ radio nuclide (Half life 15 hours ) of activity 1 micronuclids is injected into blood of a person A sample of blood of volume $\;1 cm^{3}\;$ taken after 5 hours sheemes on activity of 296 disintegration per minute. The total volume of blood in body of person is (Assume that radioactive solution mixes uniformly in blood of person . $\;(1 Ci =3.7\times10^{10} dps)$)
jeemain
physics
class12
atoms-and-nuclei
difficult
asked
Feb 26, 2014
by
yamini.v
1
answer
Light quanta with an energy 4.9 eV ejects photoelectrons from a metal with work function 4.5 eV .Then the maximum impulse transimitted to surface of metal when each electron flies out. Then de-Broglie wavelength of photoelctrons :
jeemain
physics
class12
atoms-and-nuclei
difficult
asked
Feb 26, 2014
by
yamini.v
1
answer
$S.I$. unit of inductance i.e, henry can be written as Weber divided by
jeemain
aipmt
physics
cbse
class12
ch6
electromagnetic-inductance
inductance
easy
asked
Feb 25, 2014
by
thanvigandhi_1
1
answer
If $ V_x , V_m\: and\: V_r$ respectively are the speed of X-rays, microwaves and radio waves in air, then
jeemain
aipmt
physics
cbse
class12
ch8
electromagnetic-waves
q15
easy
asked
Feb 25, 2014
by
thanvigandhi_1
1
answer
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