0
$\begingroup$

I can understand that if its a string, then since it is tired there should be a node. Also, for sound waves, since the particle near the wall cannot oscillate, there should be a node. But, in electromagnetic waves, it just has a varying electric and magnetic field. Why it should form a node at the walls ( like in radiation in a cavity)

$\endgroup$
1
$\begingroup$

The electric field parallel to a conductor must be zero. That's like "holding the string" but for electric fields.

$\endgroup$
  • $\begingroup$ But, what if the wall is not a conductor? $\endgroup$ – Indeterminate Aug 10 '17 at 14:16
  • 2
    $\begingroup$ @Indeterminate: Then the electric field parallel to the surface isn't zero, and the wall isn't a node. This what happens with EM waves passing from one transparent medium to another, and detailed analysis of that case leads to Snell's Law, the Fresnel equations, etc. $\endgroup$ – Michael Seifert Aug 10 '17 at 14:21
  • 1
    $\begingroup$ @MichaelSeifert is right: the walls of a dielectric cavity do not necessarily have a node; instead, because there is partial reflection from the interface, there will be some finite amplitude of the wave at the interface and the longest wavelength that produces resonance in the cavity will be larger than if the cavity was made from a good conductor. $\endgroup$ – Floris Aug 10 '17 at 14:27
0
$\begingroup$

Because at wall electric field and magnetic field becomes will pass through inter space between molecules so it make node with low amplitude

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.