Physics - Optics: Single Slit Diffraction (2 of 15) Basics 2: What Causes Diffraction?

[@mahadevankm2621]

Thanks Michel. I was taught this at school but I forgot about it . You repeating the concepts jogged my memory.

[@valeriereid2337]

Thanks so very much for explaining this so well.

[@MichelvanBiezen]

Glad it was helpful!

[@duduzenkie3242]

Thanks again you're the best teacher I found

[@MichelvanBiezen]

Happy to help!

[@sandorfogassy3007]

Yes, the drawing does seem confusing. It would seem that they would need to strike at the same point to have deletion.

[@mr.perfecttube6541]

You are really great!

[@MichelvanBiezen]

Thank you! 😃

[@abhiananthan7500]

Very helpful. thank you

[@ibrenecario7357]

The drawing is very bad. He tells that light will travel further , and he shows two parallel lines.....Well that is not correct. What he means is two lines that hit SAME spot on wall then one of lines would have traveled further.

[@db5837]

You are correct, he is completely incorrect. He should be comparing the length of the beam from the bottom of the slit arriving at the screen at the same point as that from the top of the slit ( an elongated triangle). The maths is more to do with interference patterns based on the wave concept of light ( Huygens' theory) rather than diffraction.

[@mrIceblink]

@@db5837 You are completely wrong. The slit width is tiny compared to the distance from the screen, the lines are parallel for practical purposes. The extra distance if you draw it exactly is a very very small fraction of even half a wavelength, so it doesn't matter for this construction.

[@euzilenepereiraneves4436]

Why 1/3 of the beam?

[@MichelvanBiezen]

At the correct angle, one third of the beam will cancel out the second third of the beam (destructive interference when the path length is one half of a wavelength more for 1/3 compared to the second third.) This way the third portion of the beam does not experience interference.

[@michaellin2382]

@@MichelvanBiezen I cannot thank you enough sir. This was the exact problem that I had when I went though my text book: what about the rest of the beams that are not cancelled out? Thank you for addressing that for me. Maybe I didn't describe my problem clearly enough but anyways, just want to say thank you so much for being an absolutely awesome Physics teacher!

[@stevetwoshedsbrough7871]

Hmmm. Gee thanks

[@fkeyvan]

It’s diffraction not die-fraction

[@MichelvanBiezen]

Thank you