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Monthly Archives: February 2016


incorporation of thermodynamics in einsteins equation

Respected sir/madam,

Can we incorporate thermodynamic concepts of enthalpy (and entropy)in Einsteins equation “E=mC2?

it will become something like:
dE/dt=C²/h (dU/dt+dW/dt)

Where ,
h= enthalpy of the system
U= total internal energy
W=total work done

is is possible?

circular motion

Is a body moving with constant angular velocity in circular path is example of accelerated motion?

Asked Prem Kumar


centripetalYes. Because acceleration is defined as the rate of change of velocity. Though the speed of a body in uniform circular motion is constant, the velocity goes on changing due to the continuous change in direction.

ultrasound and mobile communication

sir, Animals like bat and dolphins use ultrasonic sound waves to know what all are in there way , we humans also use ultrasonic sound eg- radio , mobile network etc ..

my question is that did bats like animals can here what all we talk in your mobile ?

pls avoid if it is a stupid question


Posted Sheen



We are using Microwaves/ radio waves with the audiowaves superimposed on them to communicate. (Modulation) The voice signals are modulated with MW/Radio waves and transmitted. The modulated signals are received by the antenna at receiving end and demodulated (the radio waves are removed and audio signals extracted) and the voice signals are regenerated. But in the case of bats, they are producing and hearing (or say sensing) the ultrasound just like a radar to navigate and find the prey

Polarisation – Malus Law

Two polariods P1 and P2 are placed with their pass axes perpendicular to each other. Unpolarised light of intensity Io is incident on P1. A third polariod P3 is kept between P1 and P2 such that its pass axis makes an angle of 30 with that of P1. Determine the intensity of light transmitted through P1,P2 and P3.


Asked Rashmi



Appply Malus’ Law

The intensity of light from the first polaroid P1 is Io/2

From P3, the intensity is (Io/2) cos230 =(Io/2)(3/4)=3Io/8



polarisationFrom P2, the intensity is (3Io/8)cos260= (3Io/8)(1/4)= 3Io/32

Why dispersion does not occur in a glass slab?

Why dispersion does not occur in a glass slab?
I know the reason that the opp. sides are parallel but dispersion occurs when light enters from one medium to another.. so what is the reason?prism

Asked Karan


glass slabThough there is slight dispersion when light enters glass slab at the first phase, all the colours are rendered parallel at the second phase and the different colours enter our eye without any angular separation. (Angular dispersion is the angle between the component colours and if the angle between the colours is zero, we will not see the colours)

Also read http://www.askphysics.com/why-dispersion-does-not-occur-in-a-glass-slab/


thermal properties of matter

In an experiment on the specific heat of a metal, a 0.02kg block of the metal at 150 degree celcius is dropped in a copper calorimeter(of water equivalent 0.025kg) containing 150 cubic centimetre of water at 27 degree celcius. the final temp. is 40 degree celcius.Compute the specific heat of the metal.


Asked Abel

motion in plane

The sum of magnitude of two forces acting at a point is 18N an the magnitude of their resultant is 12N.If the resultant makes an angle of 90 degree with the force of smaller magnitude what are magnitude of the two forces?

Asked Abel

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