Question

in thin film interference the positions of constructive and distructive are interchanged due to
phase coherence
phase reversal
interference
diffraction

Answer 1

Actually. Na . Interference happen because of ..phase coherent

So . It is interchange . Means interference is there. But. Position of constructive and districtive changed .

Confusion h. It may be A or B ..

Answer 2

Answer:

Phase reversal is responsible for interchange in the constructive and destructive positions in thin film interference.

Explanation:

Thin-film interference:

• The phenomenon of thin-film interference is observed when light  reflected off two surfaces of a film which is usually in microns size.
• The reflection of light depends on the relative refractive index.
• Light waves undergo a 180° phase inversion upon reflection at an interface of a medium of higher refractive index, and no change when reflecting from a lower refractive index medium.
• If the path difference between the two coherent sources equal to half wavelength, the light interfere destructively, if it is a full wavelength, then constructive interference.
• If there is no phase inversion or reversal from either surfaces of thin film, or if there is phase reversal from both surfaces then the conditions are valid.
• If there is a phase reversal at one of the interfaces but not the other, then the positions of constructive and destructive are interchanged.
• The path difference of one wavelength, results in the destructive interference due to crest interfering with the trough formed due to reversal interference. Similarly the path difference of half wavelength results in constructive interference.
• Therefore, phase reversal is responsible for interchange in the constructive and destructive positions in thin film interference.

So, the correct answer is option 2.

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