BR question on double-slits and diffraction

[ipodtouch]

Sorry, I don't seem to understand this question. Any help would be great.

A typical double-slit is actually two single slits placed near one another. The equations describing the location of the bright and dark fringes that result from two-slit interference do not take into account the diffractive effects of each single slit. This is because we assume that:
a.) single slit effects are masked by the double-slit pattern.
b.) d is much greater than (lamda)
c.) d + a is comparable to (lamda)
d.) a is comparable or smaller than lamda.

-No additional relevant information

The answer is D, and the reasoning in the explanation is that D makes diffraction effect greater and more pronounced.
I'm having trouble understanding the reasoning of this question. We don't consider "single-slit" diffraction because they are very pronounced? i thought it was just the opposite, A.

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[MedPR]

Sorry, I don't seem to understand this question. Any help would be great.

-No additional relevant information

The answer is D, and the reasoning in the explanation is that D makes diffraction effect greater and more pronounced.
I'm having trouble understanding the reasoning of this question. We don't consider "single-slit" diffraction because they are very pronounced? i thought it was just the opposite, A.

I remember this question, and there actually is "additional relevant information" in the form of exactly what "d" and "a" represent in the setup.

However, based on memory of the figure and the correct answer, I'll assume that d is the distance between the two single slits and a is the width of the slits. Answer A is incorrect because the effects of the single slits are not masked by the double-slit pattern, they are the cause of the double slit pattern. In other words, no two single slits = no double-slit pattern. Answer A is analogous to saying the direction a car turns masks the direction the driver is turning the steering wheel.

The distance between the slits isn't really relevant to this question. The only thing it determines is how far apart the light/dark fringes are on the screen. All else equal, larger slit separation = closer intensity maxima on the screen.

The only answer left is D. D is the answer because diffraction of waves is the most noticeable when the slit is smaller or at least about the same size as the wavelength.

 

[ipodtouch]

Thanks for the reply.
Yes I understand the physics of the slit experiments. But I do not understand how that means:

The equations describing the location of the bright and dark fringes that result from two-slit interference do not take into account the diffractive effects of each single slit.

 

[chiddler]

I remember this question, and there actually is "additional relevant information" in the form of exactly what "d" and "a" represent in the setup.

However, based on memory of the figure and the correct answer, I'll assume that d is the distance between the two single slits and a is the width of the slits. Answer A is incorrect because the effects of the single slits are not masked by the double-slit pattern, they are the cause of the double slit pattern. In other words, no two single slits = no double-slit pattern. Answer A is analogous to saying the direction a car turns masks the direction the driver is turning the steering wheel.

The distance between the slits isn't really relevant to this question. The only thing it determines is how far apart the light/dark fringes are on the screen. All else equal, larger slit separation = closer intensity maxima on the screen.

The only answer left is D. D is the answer because diffraction of waves is the most noticeable when the slit is smaller or at least about the same size as the wavelength.

i understand all that you wrote, but I don't understand how d is the answer (besides process of elimination). A slit's width about equal to wavelength of light which makes single slit diffraction noticeable. We assume that the slit width is about equal to wavelength so we should notice single slit diffraction. However, the question is asking why is single slit overshadowed by the double slit effect?

can you preez explain

 

[pfaction]

TPR doesn't go over this. Can you reference a page number for me from TBR?

 

[chiddler]

TPR doesn't go over this. Can you reference a page number for me from TBR?

it's the optics and light chapter in TBR.

 

[MedPR]

.

 

[ipodtouch]

So........ before this topic vanishes into oblivion.

Faulty question?

 

[brood910]

Bump. It seems like no prep books do a good job at explaining diffraction stuff.

 

[4563728]

For help on diffraction, interference, etc try these videos! This professor is amazing. Seriously, my hardest topic in physics turned into one of the most fascinating after these videos.

http://ocw.mit.edu/high-school/phys...deo/physical-optics/interference-diffraction/

Good luck 🙂

 

[brood910]

For help on diffraction, interference, etc try these videos! This professor is amazing. Seriously, my hardest topic in physics turned into one of the most fascinating after these videos.

http://ocw.mit.edu/high-school/phys...deo/physical-optics/interference-diffraction/

Good luck 🙂

Thx a bunch. I hope this vid contains more info than what TBR has.