Home » Ask & Discuss » Physics. » Modern Physics « Back to Discussion

Modern Physics

Blazing goIITian

Joined:	20 Jul 2008
Post:	610

14 Nov 2008 17:45:57 IST

0 People liked this

478

help me !!!!!!!!!!!!!!!!!!!!

None

The equivalence of mass and energy expressed by the relation E = mc² is a fairly direct consequence of Maxwell’s conception of electromagnetic waves. According to Maxwell’s equations, the energy density of electric and magnetic fields e and b is (e² + b²)/(8p) and the momentum density is (e x b)/(4pc). Thus in the case of radiation (when e and b are equal and orthogonal) the energy density is E = e²/(4p) and the momentum density is p = e²/(4pc), so we have the important relation p = E/c. In addition, the energy of a pulse of light for relatively moving systems of reference transforms in proportion to its frequency, consistent with Planck’s relation E = hn. Given these facts, we can show that light pulses of total energy E reflecting inside a closed container contribute E/c² to the inertial mass (i.e., the resistance to acceleration) of the container.

this one I got from a site.

Here it states that, electric field=magnetic field(for light)

But in the ncert physics of class 12 and many other sites it is given that

E/c=B

E=electric field

B=Magnetic field

c=speed of light

So, which is correct

Share this article on:

Comments (4)

Amith

Cool goIITian

Joined: 3 Oct 2008

Posts: 52

14 Nov 2008 17:59:04 IST

Like 0 people liked this

From Which site did u get this????????

Can u please tell that.

Madmax

Blazing goIITian

Joined: 24 Dec 2007

Posts: 1111

14 Nov 2008 19:34:19 IST

Like 1 people liked this

Its frm

http://www.mathpages.com/HOME/kmath601/kmath601.htm

Here is Ur answer.....I just tried to read a bitmore on the topic and reached this page

http://www.mathpages.com/HOME/kmath576/kmath576.htm (which as U can see by its number (576) is meant to be read before pg 601....the page U pointed out)

now whichever browser U're using, just type CTRL+F and type "equal" in the search box and do a search

U'll stumble upon this sentence:

It’s also worth noting that the radiation components of the electric and magnetic fields are equal in magnitude. To prove this, determine the squared magnitudes by taking the dot product of each vector with itself

Hope U get it now......its not for light tht the components are equal....for light it is and always will be, thanks to Prof Maxwell :

E/C=B

Its just tht for the radiation occurs equally frm the electric and magnetic components of light:

i.e. due to radiation, loss in magnetic component=loss in electric current

Also note tht this (E/C=B) is one of the fundamental considerations many physicists arbitrarily assume, since it has also been proved thru various experiments....a discovery as big as this (tht E=B) would have heralded all newspaper headlines and guarenteed a Nobel prize for researchers who proved it!! We'd have to completely redefine Physics if E=B (just realised one case when E can be equal to B......at E=B=0 but then this is also true for E=CB so its redundant!!)

hope this helps

cheers!!

Protyush Sahu

Blazing goIITian

Joined: 20 Jul 2008

Posts: 610

14 Nov 2008 21:36:30 IST

Like 0 people liked this

Thanx a lot madmax !!!!!!!!!!!!!!!!!!!

Madmax

Blazing goIITian

Joined: 24 Dec 2007

Posts: 1111

15 Nov 2008 11:37:46 IST

Like 0 people liked this

my pleasure!! Tht's wht we're here for...to help each other through confusing times!!

cheers!!

Quick Reply

Reply

	Some HTML allowed.
	Keep your comments above the belt or risk having them deleted.
	Signup for a avatar to have your pictures show up by your comment
	If Members see a thread that violates the Posting Rules, bring it to the attention of the Moderator Team