Interference Between Two Glass Plates

Physics Ninja looks at the interference between 2 glass plates.

[@MrMegaL0N3]

Good insight. Considering the air gap wedge as comprised of similar triangles certainly adds clarity to this problem.

[@RobertDuffin-c4u]

Why not consider reflection of light off the top surface of the top layer of glass?

[@orca_ah]

thank you for the video! I was confused a lot about why light does not get phase shift when it gets reflected from the first glass, but then i realized thanks to your explanation that we are considering only the light that has passed through the first glass and not reflected from it. Thank you

[@claytonhouser7578]

Why is there no reflection when you first enter the top glass???

[@myloveispunk]

Thanks for making this clear, this is a very abstract concept.

[@Arnav-ov5rx]

Why did we not take reflection from top surface of top face?

[@karensc6747]

what would change if the two glass plates would be placed parallel? Because in this case i cannot use trigonometric relations

[@kwabenasody1218]

Please how come the yellow light ray that goes back into the first plate, doesnt get inverted or a phase shift.?...... i understand the first yellow ray will have a phase shift when its hits off the surface of the second plate..... so why not the second ray

[@amrmahmoud7231]

Thank you for your video It’s really helpful What is the effect of theta please on the fringes?

[@shonab7618]

Really helpful, but I still don't understand why you find the spacing between the dark fringes - how does that help you determine the width of the object?

[@senivoliliratuvuki6679]

How to calculate the spacing of dark fringes in the interference reflected from the air wedge

[@abdallahmohamedelhady6668]

Thank you very much

[@AnishaSingh0914]

why doesn't the light reflect off the bottom of the bottom plate? why are we choosing to ignore that, how would I know not to use that

[@suhasthanmay2114]

Thank you sir

[@kumaneko50732]

when x=0 shouldn’t thelight be constructively interfering because id y=0 the ‘transmitted’ ray never travels through the air pocket and doesnt get phase shifted?

[@tingsen7370]

Thank you!

[@siddharthshewale1205]

Does the light not also get refracted by the bottom glass and reflect off the bottom not the top, just like the top glass did

[@PhysicsNinja]

Yes, absolutely. You can create multilayers where you would have to consider the reflections and refractions off each surface. For this problem I only consider the simplified case (assume that the bottom plate is really thick, although the picture doesn't show this).

[@ruicampos8631]

3:18 - How come? The light ray clearly has a path lenght greater than 2y.

[@PhysicsNinja]

Yes the path length is longer than 2y but the for interference the only thing that matter is the path difference.

[@Pyrodeity42]

Why doesn't the light reflected off the top part of the top plate matters?

[@jaechng]

idk

[@Pyrodeity42]

@@jaechng lmao hi

[@danamomani7461]

why are we solving for x

[@danamomani7461]

how come x is the interfringal distance

[@PhysicsNinja]

Sometimes the problem is used to find the diameter of hair at the end of the glass slides. If you know the spacing between fringes you can then easily for the diameter. Good luck!

[@danamomani7461]

Physics Ninja i understand, but how come x is the spacing between the fringes

[@PhysicsNinja]

Dana Momani because when n=0 the position is x=0, when n=1 that is the position of the next fringe x=1.25mm and so on.

[@adityaaggarwal3503]

Are you left handed :p

[@waynebao5959]

I love you

[@ghostrider0266]

gayyy

[@kacpersuchecki2188]

You're wrong. You do a big mistake!! If you thinking about the light which have 500nm wavelenght you can"t aproximate that destructive and interfirence will be for 2y=n*lambda and for construcitive 2y=...... Difrence between two beams is not equal to "2y" and for so small wavelenght it's a big mistake.

[@PhysicsNinja]

LOL! do the math it's only 40 wavelength (500nm/0.02mm)

[@kacpersuchecki2188]

@@PhysicsNinja in this case yes but, when angle is bigger and and lenght between two surface is much longer it making bigger error. For example If you measure flatness of surface by interferometry with air wedge this error can make wrong result.

[@PhysicsNinja]

@@kacpersuchecki2188 this video is not meant to capture every case. Every physics problem has a lot of approximation and there are too many to list. This is a quick way to take 2 glass slides and measure the diameter of your hair.

[@kacpersuchecki2188]

Once time you tell that difference beetween those two beams patchs is aproximatly 2y. Next time you said for destructive interference 2y is "equal" to n*lambda. It can be misunderstood by someone. If you make condition write that this isn't equal but approximate. You can calculate for this example like equal. But conditions are not only for this example. If you didnt write that this condition is true only for angle nearly zero and small lenght beetween surface or aproximate the condition will be false.