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JEE · Physics · Wave Optics doubts

8 doubts found

JEEPhysicshard

Why does a soap bubble or a film of oil on water show swirling rainbow colours?

Light reflects off both the top and bottom surfaces of the thin film.

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JEEPhysicshard

In Young's double-slit experiment, what happens to the fringes if I move the slits closer together?

Fringe width is β = λD/d, so it's inversely proportional to the slit separation d.

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JEEPhysicshard

If I do the double-slit experiment underwater, do the fringes change?

Yes.

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JEEPhysicshard

Why does light passing through a single very narrow slit spread into a broad bright band instead of a sharp line?

That's single-slit diffraction: every point of the slit acts as a wavelet source, and these wavelets interfere.

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JEEPhysicshard

How do Polaroid sunglasses cut the glare off water and roads?

Light reflected off horizontal surfaces (water, wet roads, car bonnets) is mostly polarised horizontally.

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JEEPhysicshard

Why can't the headlights of two different cars ever produce an interference pattern?

Interference needs coherent sources — a constant phase relationship.

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JEEPhysicseasy

What does “Coherence” actually mean in Wave Optics, and why does it matter for JEE?

two sources are coherent if they keep a constant phase difference — a must for a steady interference pattern.

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JEEPhysicsmedium

I keep getting “Coherence” questions wrong in Wave Optics. What's the trap?

expecting two ordinary bulbs to interfere.

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