Recent questions in Physics

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.

asked Feb 27, 2014 by thanvigandhi_1

1 answer

The wavelength of a radio wave of frequency of $1\: MHz$ is:

asked Feb 27, 2014 by thanvigandhi_1

1 answer

Which of the following are not electromagnetic waves?

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 .

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 :

asked Feb 27, 2014 by yamini.v

1 answer

The radii of two nuclei with atomic ratio of no .1 & 27 is ?

asked Feb 27, 2014 by yamini.v

1 answer

Which of following are not deflected by a magnetic field ?

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

asked Feb 27, 2014 by yamini.v

1 answer

Mark the correct option

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}$

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?

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 =$\;1.67\times10^{-27} Kg$) .

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 .

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:

asked Feb 27, 2014 by thanvigandhi_1

1 answer

Electromagnetic waves are transverse in nature is evident by

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 $\;(lithium\;M_{li}=7.016 u)\;$

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 $\;1.02 \%\;(log_{10}^{1.02}=0.0086)$

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 .

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

asked Feb 27, 2014 by yamini.v

1 answer

Infrared radiation is detected by

asked Feb 26, 2014 by thanvigandhi_1

1 answer

The electromagnetic waves that stimulate blood circulation are

asked Feb 26, 2014 by thanvigandhi_1

1 answer

The oscillating electric & magnetic vectors of an electromagnetic wave are oriented along

asked Feb 26, 2014 by thanvigandhi_1

1 answer

$UHF$ range if electromagnetic waves can be propagated by means of

asked Feb 26, 2014 by thanvigandhi_1

1 answer

Electromagnetic waves are produced by:

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)

asked Feb 26, 2014 by thanvigandhi_1

1 answer