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More on single slit interference

Continue to explore the phenomenon of single slit interference. See how there's actually constructive (rather than just destructive) interference at some points on the screen. single slit interference, a complex phenomenon in light physics. Learn about the mathematical reasoning behind destructive points and why it doesn't apply to constructive points, and relate this to diffraction gratings, phase differences, and the challenge of finding exact locations of constructive points. Created by David SantoPietro.

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• so is there an actual constructive spot in the very center where you have that large large peak?
• Correct. You can see this by looking at the formula.
Where theta=0 there will be no path difference. Consequently, there will be no way for the two wave fronts to get out of phase, and they therefore interfere constructively.
• What is the reason we get any additional constructive points besides the middle peak? If there are destructive interferences everywhere, why do we still see a pattern of peaks rather than just one peak in the middle?
• Because they are not completely destructive everywhere. Where they are completely destructive there we see a dark spot. And in other places we find mild bright places.
• At why are the waves in different phases? Aren't they from the same source?
In the double slit experiment we assumed that they are from the same source since they originate from the same laser, so why not here as well?
• Because they are travelling different distances.
• Oh! I'm super cooper CONFUSED!!
Is the bright spot in the middle made of constructive or destructive waves? If destructive waves cancel each other out as said in the first video,then how do they form a spot out there on the screen?
• Good question

Lets start by saying that ALL waves can be constructive and destructive; it depends on the way that they meet. Have a look at the topic again just to get really clear,

For the bright spot (or 'central maximum' this is where the waves will be meeting in a constructive way. (ie they are IN PHASE). If they were meeting in a totally destructve way, then there would be a dark spot. (ie a MINIMUM)

:-)
• if one peak meets one crest then they cancel out each other,is this violate the law that energy cannot be created nor destroyed since light is a form of energy?
• Nope ,
When a crest and a trough from two travelling wave meets , they just cancel out each other at that moment , after that specific moment there will be two waves again.

In a interference pattern , there are constructive and destructive interference points , making the energy(amplitude) at some points being " cancelled " while some being " doubled " , make the system's net energy not changing.
• I am full on lost
• what's the differrance between single slit interference and diffraction grating?
they both have independant waves in very short distance and i cant find the differance between placing many holes on the board to make many waves and considering wave as a group of independant waves
• A diffraction grating has many, many slits. Why don't you watch the videos about the double slit and the diffraction grating.