Recent questions tagged ncert

The normal activity of living carbon containing matter is found to be about 15 decays /min for every gram of carbon . This activity arises from the small proportion of radioactive $_6C^{14}$ present with the ordinary $_6C^{12}$ isotope. When the organism is dead , its interaction with the atmosphere Which maintains the above equilibrium activity ,ceases and its activity begins to drop. From the known half life $(=5730 years) $ of $_6C^{14}$ and the measured activity , the age of the specimen can be approximately estimated the approximate age of the Indus valley civilization

asked Jul 12, 2016 by meena.p

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A radio active isotope has a half of T years. How long will it take the activity to reduce to $1\%$ of its original activity .

asked Jul 12, 2016 by meena.p

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A radio active isotope has a half of T years. How long will it take the activity to reduce to $3.125\%$

asked Jul 12, 2016 by meena.p

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Write nuclear reaction equation for Electron capture of $_{54}X_e^{120}$

asked Jul 12, 2016 by meena.p

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Write the nuclear reaction equation for $\beta^{+}$ decay of $_{43}Tc^{97}$

asked Jul 12, 2016 by meena.p

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Write the nuclear reaction equation for $\beta^{+}$ decay of $_{6} C ^{11}$

asked Jul 12, 2016 by meena.p

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Write nuclear equation for $\beta^{-}$ decay of $_{83} Bi ^{210}$ $\beta^{-}$ decay of $_{83} Bi ^{210}$

asked Jul 12, 2016 by meena.p

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Write nuclear equation for $\beta^{-}$ decay of $_{11} P ^{32}$

asked Jul 12, 2016 by meena.p

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Write nuclear equation for $\alpha$ decay of $_{94} Pu ^{242}$

asked Jul 12, 2016 by meena.p

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Write the nuclear reaction for $\alpha$ delay of $_{88} Ra^{226}$

asked Jul 12, 2016 by meena.p

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A given coin has a mass of 3 o.g calculate the nuclear energy that would be required to separate all the neutrons and protons from each other . For simplicity assume the coin is entirely made of $_{29} Cu ^{63}$ atom (of mass 62.92960u)

asked Jul 12, 2016 by meena.p

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Obtain the binding energy of the nuclei $_{26} Fe^{56}$ and $_{23} Bi ^{209}$ in units of Mev from the following data $m_H= 1.007825\;amu\;m_n= 1.008665\;amu \; m( _{26} Fe ^{56})=55.934939 \;amu\; m( _{83} Fe ^{209})=208.980388 \;amu\;lamu=931.5\;Mev$ Which nucleus has greater binding energy per nucleon ?

asked Jul 11, 2016 by meena.p

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Obtain the binding energy of a nitrogen nucleolus $(_7N^{14})$ from the following data $m_n=1.00783 \;amu \; m_n =1.00867$ amn , $m_n=14.00307 \;amu$ give your answer in Mev

asked Jul 11, 2016 by meena.p

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The three stable isotopes of neon :$Ne^{20}, Ne^{21},Ne^{22}$ have respective abundances of $90 .51 \%, 0.27\%$ and $9.22\%$ . The atomic masses of three isotopes are $19.99$ amu , $20.99\;amu$ and $21.99\;amu$ Obtain the average atomic mass of neon .

asked Jul 11, 2016 by meena.p

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Boron has two stable isotope, $_5 B^{11}$ and $_5 B^{11}$ Their respective masses are $10.01294 \;amu$ and $11.00931\;amu$ and the atomic weight of Boron in $10.811\;amu$ . Find the abundances of $_5B^{ 10}$ and $_5B^{11}$

asked Jul 11, 2016 by meena.p

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Two Stable isotopes of lithium $^6_3Li$ and $^7_3 Li$ have respective abundances of $7.5\%$ and $92.5 \%$ These isotopes have messes $6.01512$ amu and $7.01600$ amu respectively . Find the atomic height of lithium

asked Jul 11, 2016 by meena.p

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Taking the Bohr radius as $a_0 = 53 \;pm, $ the radius of $Li^{++}$ ion in its ground state , on the basic of Bohr's model will be about

asked Jul 6, 2016 by meena.p

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The total energy of electron in the first electron state of hydrogen atom is about $-3.4\;ev$ What is the kinetic energy of electron in this state ?

asked Jul 6, 2016 by meena.p

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Is the average angle of deflection of $ \alpha$ particles by a thin gold foil predicted by Thomson's model much less , about the same or much greater than that predicted by Rutherford's atom model ?

asked Jul 6, 2016 by meena.p

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In accordance with the Bohr's model find the quantum number that characterizes the earth revolution around the sun in an earth orbit of radius $1.5 \times 10^{11}\;m$ with orbital speed $3 \times 10^4 \;ms^{-1}$

asked Jul 6, 2016 by meena.p

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A $12.5\;ev$ electron beam is used to bombard gaseous hydrogen at room temperature .What series of wave length will be emitted ?

asked Jul 6, 2016 by meena.p

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The radius of inner most electron orbit of a hydrogen atom is $5.3 \times 10^{-11}\;m $ what are the radii of $n=2$ and $n=3$ orbits?

asked Jul 6, 2016 by meena.p

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Using Bohr's model , calculate the orbital period of the electron in a hydrogen atom in the $n= 1,2$ and $3$ levels

asked Jul 6, 2016 by meena.p

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Using the Bohr's model , calculate the speed of the electron in a hydrogen atom in the $n= 1,2$ and 3 levels

asked Jul 6, 2016 by meena.p

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A hydrogen atom initially in the ground level absorbs a photon, which excites it to $n=4$ level. Determine the wave length and frequency of photon .

asked Jul 6, 2016 by meena.p

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The ground state energy of hydrogen atom is $-13.6 ev$ what are the kinetic and potential energies of the electron of the electron in this state ?

asked Jul 5, 2016 by meena.p

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A difference of $2.3 \;ev$ separates two energy levels in an atom. What is the frequency of radiation emitted when the atom transmit from the upper level to the lower level .

asked Jul 5, 2016 by meena.p

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What is the shortest wave length present in the paschen series of spectral lines ?

asked Jul 5, 2016 by meena.p

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Suppose you are given a chance to repeat the alpha particle scattering experiment using a thin sheet of solid hydrogen in place of gold foil (hydrogen is a solid at temperature below 14 k) What results do you except ?

asked Jul 5, 2016 by meena.p

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The positively charged part of the atom possesses most of the mass of the atom in __________

asked Jul 5, 2016 by meena.p

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An atom has a nearly continuous mass distribution in but has a highly non uniform mass distribution in ____

asked Jul 5, 2016 by meena.p

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A classical atom based on _________ is doomed to collapse

asked Jul 5, 2016 by meena.p

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In the ground state of __ electrons are in stable equilibrium , while in electrons always experience a net force

asked Jul 5, 2016 by meena.p

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The size of the atom in Thomson's model is __________ the atomic size in Rutherford's model

asked Jul 5, 2016 by meena.p

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A Proton , a neutron , an electron and an $\alpha$ particle have same energy.Then their de Broglie wave length compare as :

asked Jul 4, 2016 by meena.p

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The wave length of a photon needed to remove a proton from a nucleus which is bound to the nucleas with 1 Mev energy is nearly

asked Jun 30, 2016 by meena.p

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The energy and momentum of an electron are related to the frequency and wave length of the associated matter wave by the relation $E= h \gamma,P=\large\frac{h}{\lambda}$ But while the value of $\lambda $ is physically significant the value of $\gamma$ (and therefore the value of phone speed ) has no physical significance why ?

asked Jun 30, 2016 by meena.p

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Every metal has a definite work function. Why do all photo electrons not come out with the same energy if incident radiation is monochromatic ? why there an energy distribution of photo electron ?

asked Jun 30, 2016 by meena.p

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Why should gases be insulators at ordinary pressures, and start conducting at low pressures.

asked Jun 30, 2016 by meena.p

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What is so special about the combination e/m ? Why do we not simply talk of e and m separately ?

asked Jun 29, 2016 by meena.p

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Quarks inside protons and neutrons are through to carry factional charges $\bigg[+\bigg( \large\frac{2}{3}\bigg):\bigg( \large\frac{-1}{3}e\bigg)\bigg]$ why do they not show up in Millikan's oil-drop experiment ?

asked Jun 29, 2016 by meena.p

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Compute the typical de-Broglie wave length of an electron in a metal at $27^{\circ}$ C and compare it with the mean separation between two electron in a metal which given to be about $2 \times 10^{-10}\;m$

asked Jun 29, 2016 by meena.p

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Find the typical de- Broglie wave length associated with a Helium gas at room temperature $(27^{\circ})$ and latm pressure, and compare it with the mean separation between two atoms under there conditions .

asked Jun 29, 2016 by meena.p

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The wave length of an probe is volubly a measure of the size of a structure that it can probe in some detail. The quark structure of protons and neutrons appear at the last minute length - scale of $10^{-5}\;m$ or less. This structure was first probed in early 1970's using high energy electron beam produced by a linear acceleration at stanford USA. guess what might have been the order of energy of these electron beams . (Rest mass energy of electron $=0.511\; Mev$)

asked Jun 29, 2016 by meena.p

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An election micro scope uses electrons accelerated by a voltage of 50 kv. Determined the de-Broglie wave length associated with the electrons. If other factor (such as numerical aperture ) are taken to be roughly the same, how does the resolving power of an electron microscope that uses yellow light ?

asked Jun 28, 2016 by meena.p

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Obtain the de-Broglie wave length associated with thermal neutrons at room temperature $27^{\circ}$ Hence explain why a fast neutron beam needs to be thermalised with the environment before it can be used for neutron diffraction experiments.

asked Jun 28, 2016 by meena.p

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Obtain the de- Broglies wave length of a neutron of kinetic energy $150\;ev$ would a neutron beam of same energy be equally suitable for crystal diffraction experiments ? Explain given $m_n= 1.6 \pi \times 10^{-27}\;kg$

asked Jun 28, 2016 by meena.p

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Crystal diffraction experiment can be performed using x- rays or electron acceleration through appropriate voltage ? Which probe has grater energy ? An x -ray photon or the electron ?

asked Jun 28, 2016 by meena.p

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Light of intensity $10^{-5} \;wm^{-2} $ falls on a sodium photocell of surface area $2 cm^2$ Assuming that the top 5 layers of sodium absorb the incident energy, estimate the time required for photo electric emission in the wave picture of radiation . The work function of the metal is given to be about 2 ev . What is the implication of your answer ? Effective atomic area $=10^{-20} m^2$

asked Jun 28, 2016 by meena.p

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The work function for the following metals is given $Ni: 5.15 \; ev$ What happen if the laser is brought never and placed 50 cm away ?

asked Jun 28, 2016 by meena.p

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