Recent questions in Atoms

In an experiment of photoelectric effect , singly ionized helium is excited electronically to different energy levels. The emission spectra of helium produced is incident on a photo - electric plate in photocell .When helium is excited to fourth energy - level than the observed stopping potential of photocell is found to be five times stopping potential when hydrogen is excited to third level . Then the work function of material of photo-electric plate is

asked Feb 25, 2014 by yamini.v

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A gas of identical hydrogen like atoms has some atoms in lowest (ground) energy level A and some atoms in a particular upper (excited) energy , level B and there are no atoms in any other energy level . The atoms of gas make transition to higher energy level by absorbing monochromatic light photon having energy 2.7eV . Subsequently the atoms emit radiation of only six different photon energies . Some of emitted photons have energy 2.7eV some have energy more and some have less than 2.7eV . Then the principal quantum no .of initially excited level B is

asked Feb 25, 2014 by yamini.v

1 answer

A $\;^{118}cd\;$ radionuclide goes through transformation chain $\;^{118}Cd\; \to_{30 min}^{118}ln \to_{45 min} ^{118}Sn\;$(stable) The half lives are written below respective arrows ,A time t=0 only celuear present. Then the fraction of nuclei transformed into stable over 60 minutes:

asked Feb 25, 2014 by yamini.v

1 answer

Masses of two isobars $\;_{29}^{64}Cu\;$ and $\;_{30}^{64}Zn\;$ are 63.9298n and 63.9292n respectively.It can be concluded from these data that

asked Feb 25, 2014 by yamini.v

1 answer

A monochromatic radiation wavelength $\;\lambda_{1}\;$ is incident on a stationary atom as a result of which wavelength of photon after collision becomes $\;\lambda_{2}\;$ and recoiled atom has De- Broglie's wavelength $\;\lambda_{3}\;$.Then

asked Feb 25, 2014 by yamini.v

1 answer

The ratio of de-Broglie wavelength of moleculus of hydrogen and helium in two gas jars kept separately at temperatures $\;27^{0} C\;$ and $\;127^{0} C\;$ respectively is

asked Feb 25, 2014 by yamini.v

1 answer

The ratio of de-Broglie wavelength of a $\;\alpha\;$ particle to that of proton being subjected to same magnetic field so that the radii of their path are equal to each other assuming the field induction vector $\;\overrightarrow{B}\;$ is perpendicular to velocity vectors of $\;\alpha-\;$ particle and proton , is

asked Feb 25, 2014 by yamini.v

1 answer

If a stationary electron gets annihilated due to association with a stationary positron (hypothetically), the wavelength of resulting radiation will be .

asked Feb 25, 2014 by yamini.v

1 answer

When a metallic surface is illuminated with monochromatic light of wavelength $\;\lambda\;$ and stopping potential for photo electron current is $\;3V_{0}\;$ . When some metallic surface is illuminated with a light of wavelength $\;2 \lambda\;$ , The stopping potentials is $\;V_{0}\;$ . The threshold wavelength for surface is

asked Feb 25, 2014 by yamini.v

1 answer

A photon of wavelength $\;5030 A^{0}\;$ is incident on a totally reflecting surface. The momentum delivered by photon is equal to

asked Feb 25, 2014 by yamini.v

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A star initially has $\;10^{40}\;$ deutrons . If produces energy via the process $\;_{1}H^{1}+_{1}H^{2} \to _{1}H^{3}+P\;$ and $\;_{1}H^{2}+_{1}H^{3} \to _{2}He^{4}\;.$ If the average power radiated by star is $\;10^{16}W\;,$ the deutron supply of star is exhausted in a time of order of \[\] (The masses of nuclei are $\;m(H^2)=2.014\;amu\;,m(p)=1.007 amu , \; m(n)=1.0084 amu ,\; m(H)=4.001 amu))$

asked Feb 25, 2014 by yamini.v

1 answer

Binding energy per nucleon vs mass no . Curve for nuclei is shown in figure. W,X,Y,Z are four nuclei indicated on curve . The process that would release energy is

asked Feb 24, 2014 by yamini.v

1 answer

The weight based ratio of $\;U^{238}\;$ and $\;Pb^{226}\;$ in a sample of rock is 413 . if the half life of $\;u^{238}\;$ is $\;4.5 \times10^{9}\;years \;,$ then age of rock is

asked Feb 24, 2014 by yamini.v

1 answer

A hydrogen atom is in an excited state of principal quantaum number$\; (n)\;$ it emits a photon of wavelength $\;(\lambda)\;,$ when it returns to ground state . The value of n is

asked Feb 24, 2014 by yamini.v

1 answer

There are two radioactive substance A and B . Decay constant of B is two times that of A . Initially both have equal no.of nuclei . After n Lay liver of A rate of disintegration of both are equal . The value of n is

asked Feb 24, 2014 by yamini.v

1 answer

If stationary proton and $\;\alpha-\;$ particle dre accelerated through same potential difference , the ratio of Debrogle's wavelength will be

asked Feb 24, 2014 by yamini.v

1 answer

The wavelength of $\;K_{\alpha}\;$ X-ray produced by X-ray to be is 0.76$A^{0}\;$. The atomic no.of anticathode material is

asked Feb 24, 2014 by yamini.v

1 answer

The ratio of minimum to maximum wavelengths of radiation that an electron cause in Bohr's hydrogen atom is

asked Feb 24, 2014 by yamini.v

1 answer

Radio isotopes of phosphorous $\;P^{32}\;$ and $\;P^{35}\;$ are mixed in ratio of 2:1 of atoms .The activity of samples 2 $\;\mu Ci\;$.Find activity of sample after 30 days. $\;t_{\large\frac{1}{2}}\;$ of $\;P^{32}=14\;$days and $\;t_{\large\frac{1}{2}}\;$ of $\;P^{33}\;$ is 25 days.

asked Feb 24, 2014 by yamini.v

1 answer

The mean lives of an radio active substance are 1620 and 405 years for $\;\alpha-\;$emission and $\;\beta-\;$ emission respee. Find out time during which three fourth of a sample will decay if it is decaying both the $\;\alpha-\;$emission and $\;\beta-\;$ emission simultaneously

asked Feb 24, 2014 by yamini.v

1 answer

It is proposed to use nuclear fusion reaction : $\; _{1}H^{2}+_{1}H^{2}=\;_{2}He^{4}\;$ in a nuclear reactor of 200MW rating . If energy from above reaction is used with a $\;25 \%\;$ efficiency in reactor how many gr ams of deuterium will be needed per day . (The masses of $\;_{1}H^{2}\;$ and $\;_{2}He^{4}\;$ are 2.0141 & 4.0026 amu respectively

asked Feb 24, 2014 by yamini.v

1 answer

uranium ores on earth at present time typically have a composition of $\;99.3 \%$ of isotope $\;_{92}U^{238}\;$ and $\;0.7 \%\;$ of isotope $\;_{92}U^{235}\;$. The half lives of these isotopes are $\;4.47 \times10^{9}y\;$ and $\;7.04\times10^{8}y\;$ respectively . If these isotopes were equally abundent when the earth was formed , estimate the age of earth .

asked Feb 24, 2014 by yamini.v

1 answer

The activity of a radiooctine sample is measured as 4750 counts/min at $\;t=0\;$ and as 2700 counts/min at $\;t=5$ minutes . Calculate Lay life of sample

asked Feb 24, 2014 by yamini.v

1 answer

A deuterium reaction that occurs in an experimental fusion reactor is in two stapes \[\] (1) Two deuterium nucli fuse together to form a tritium nucleus , with a proton as a by-product written as $\; 1 > (D ,P)\; T\;.$ \[\] (2) A tritium nucleus fuses with another oleunterium nucleus to form a helium $\;_{2}He^{4}\;$ nucleus with neutron as a-by-product written as $\;T (D,n)\;_{2}He^{4}\;.$ Then the energy released in each of two stages and energy released in combined reaction is \[\] Given \[\] $\;_{1}D^{2}=2.014102\;a.m.u $ \[\] $\;_{1}T^{3}=3.016049\;a.m.u$ \[\] $\;_{1}H^{1}=1.007825\;a.m.u$ \[\] $\;_{1}n^{1}=1.008665\;a.m.u$\[\] The energy released per deuterium nuclei is

asked Feb 24, 2014 by yamini.v

1 answer

A deuterium reaction that occurs in an experimental fusion reactor is in two stapes \[\] (1) Two deuterium nucli fuse together to form a tritium nucleus , with a proton as a by-product written as $\; 1 > (D ,P)\; T\;.$ \[\] (2) A tritium nucleus fuses with another oleunterium nucleus to form a helium $\;_{2}He^{4}\;$ nucleus with neutron as a-by-product written as $\;T (D,n)\;_{2}He^{4}\;.$ Then the energy released in each of two stages and energy released in combined reaction is \[\] Given \[\] $\;_{1}D^{2}=2.014102\;a.m.u $ \[\] $\;_{1}T^{3}=3.016049\;a.m.u$ \[\] $\;_{1}H^{1}=1.007825\;a.m.u$ \[\] $\;_{1}n^{1}=1.008665\;a.m.u$

asked Feb 24, 2014 by yamini.v

1 answer

How much energy must a bombarding proton possess to cause the reaction ? $\;^{7}H_{3}+^{1}H_{1} \to _{4} Be^{7}+_{0}n^{1}$

asked Feb 23, 2014 by yamini.v

1 answer

The binding energy of $\;_{17}cl^{35}\;$ nucleus is 298 HeV . Find its atomic mass $\;(_{1}H^{1})\;$ is 1.008143 a.m.u and that of a neutron is 1.008986 a.m.u . Given $\;1amu=931 MeV\;$

asked Feb 23, 2014 by yamini.v

1 answer