Thin films.

Please xplain the mechanism of interference through thin films.

14 Answers

1
skygirl ·

no new mechanism.
only sum more path difference is introduced.
this is calculated as t(μ-1)....
μ=refractive index of the film

let the total path diff be= Δx.

if Δx=nλ →constructive interference
if Δx=(n+1/2)λ →destructive interference

1
voldy ·

diagram needed.

1
voldy ·

See nishant , our sir , told to seprate ,the rays ,he siad take the ray 1,2 as reflected rays and rays 3,4 as transmitted.
then he gave the condition for constructive interference of the reflected rays and trnsmitted rays.

I feel , what ever is not reflected is transmiteed and vice versa . So gettign confused.What's your method?
Please give it . Help me understnad it . I don't follow HCV conventions.
i.e. +ve left or right? or somehitng like that . I follow real +ve
virtuall -ve . Please give me the concept.
properly. better if you tell it tottally.

1
voldy ·

I'm a idiot , I don't know why I wrote abt conventions in the firstplace? Ignore that.

62
Lokesh Verma ·

see srinath..

ur sir told the right thing..

the reflected rays are some of the incident rays...

It is not the u can incident only 1 ray at a time. In fact it is not practically possible. It has to be a beam of light!

So ur doubt is correct in a sense.. But incorrect in another.

Actually I dont remember correctly but I think that for teleportation experiment.. it was based on a single light ray which got both reflected and transmitted! (Dont accept this immediately.. and anyway this is not in syllabus)

1
voldy ·

but he said questions on these and air wedges have been asked.

62
Lokesh Verma ·

i din get u?!

1
voldy ·

NO , Isn't ray 2 a tranmitted one . and ray 4 a reflected one.?

1
voldy ·

Ok ,take a beam .Do whatever you want , but explain.Please

62
Lokesh Verma ·

it is and it is not..

Ray 2 is transmitted first.. and gets reflected on the 2nd surface and gets transmitted again through the first surface..

But for someone standing in front of the mirror. It will be like the ray was reflected...

So for the person standing in front of the mirror, if these rays undergo destructive interference, he will not see anything!

That is probably what ur sir wanted to explain to u...

ditto with the transmitted rays 3 and 4

1
skygirl ·

there is always a path difference of π added wenever thr is a reflection at some point.

1
voldy ·

Isn't the path difference added only when reflection takes place from , Denser mdm . According to EM theory.

1
skygirl ·

yup. but u didn mention the refractive indices so i jus told in general....

1
voldy ·

xplain again , what mirror ? I didn't get you ?

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