Phase Diff: Why Does 180° Change Occur?

[sheld]

Why phase difference of EM wave is changed 180 degrees reflected from denser medium?
I will be glad if u give me the actual reason [emoji4]

 

[rumborak]

The answer depends somewhat on your knowledge of the matter.

The simplest answer is that the boundary behaves as a classic "hard boundary" that a wave gets reflected from:

http://www.acs.psu.edu/drussell/Demos/reflect/reflect.html

 

[sheld]

Thanks for ur help to provide this link... though I have little bit confusion, I will figure it out..

 

[sophiecentaur]

Why phase difference of EM wave is changed 180 degrees reflected from denser medium?
I will be glad if u give me the actual reason [emoji4]

The 'reason' can be explained in terms of a change of impedance and the requirement for continuity at the boundary. At the interface, there has to be continuity of E and H fields - as a wave crosses, if the ratio of E/H changes (different phase velocity) then there must be a reflected wave because all the energy can't pass through. One or other of the Electric or Magnetic fields in the reflected wave will be in anti phase so that there is no change in field across the boundary. Which one changes sign, depends on whether the impedance of the second is greater or less than the impedance of the first medium.
This link may help or, maybe this one.

 

[sheld]

Thanks for ur link [emoji4]

 

[Leesa Johnson]

An electromagnetic wave undergoes a phase change of 180° upon reflection from a medium that has a higher index of refraction than the one in which the wave is traveling.

 

[sophiecentaur]

An electromagnetic wave undergoes a phase change of 180° upon reflection from a medium that has a higher index of refraction than the one in which the wave is traveling.

The OP wants a reason / explanation, though. Why would you expect the reflection from a lower index of refraction boundary to be in phase?