Diffraction Grating Multiple Choice Questions

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The discussion revolves around multiple choice questions related to diffraction grating and the Huygens-Fresnel principle, with a user seeking help to prepare for an upcoming exam. Key questions include the effects of covering a slit in a double slit experiment and the applicability of the Huygens-Fresnel principle in various contexts. Participants emphasize the importance of understanding light patterns produced by slits and the conditions for resolving two point-like sources in a telescope. The conversation encourages the user to attempt answering the questions independently and to utilize textbooks or online resources for better comprehension. Overall, the thread highlights the need for foundational knowledge in wave optics to tackle the exam questions effectively.
pari786
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Hey, I have to answer the following multiple choice questions ... its relevant to my exam which is day after tomorrow. Can anyone please tell which options should be the answers and why... I don't have any clue about these. So please don't delete this post ... instead please help me to pass the exam. I'll never forget your guy's help. Thanks

Covering up one of the slits on a double slit experiment would have which of the following effects?

a. The larger pattern would get slightly smaller
b. The small pattern within the larger pattern would get slightly larger
c. The larger pattern would disappear
d. The smaller pattern within the larger pattern would disappear
e. The small angle approximation would no longer be valid


The Huygens-Fresnel principle tells us to pretend that each point of a wavefront in a slit or aperture is a point source of light emitting a spherical wave. Is this true only for points inside the slit? What if there is no slit? The Huygens-Fresnel principle really applies

1. to any point anywhere in a beam path.
2. to any point in a beam path where matter is present.
3. only in slits or apertures.


If the Huygens-Fresnel principle applies to any point anywhere in a beam path, why doesn’t a laser beam without any slit spread out in all directions?

1. Because all waves that spread interfere destructively.
2. It does spread, but the spread is so small that we normally don’t notice it.
3. We can’t apply the Huygens-Fresnel principle anywhere but in slits and apertures.


Light waves from two point-like sources arrive at the circular aperture of a telescope simultaneously. The telescope will resolve the two sources if which of the following conditions is satisfied?


1. the Fresnel approximation
2. the Fraunhofer approximation
3. the Huygens-Fresnel principle
4. the Rayleigh criterion
 
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What do you think the answers might be and why? :smile:

Some things to consider:

1) What light pattern does a single slit produce?
2) Does your textbook show a sketch illustrating the Fresnel Huygens principle, and if so, what does it show?
3) Is the end of the laser cavity a kind of circular slit?
4) What does it really mean to be able to "resolve" two points?
 
JeffKoch said:
What do you think the answers might be and why? :smile:

Some things to consider:

1) What light pattern does a single slit produce?
2) Does your textbook show a sketch illustrating the Fresnel Huygens principle, and if so, what does it show?
3) Is the end of the laser cavity a kind of circular slit?
4) What does it really mean to be able to "resolve" two points?

I already said that I don't know anything about this stuff. :cry: :cry:
 
Then if you don't try, you'll deserve to flunk. :smile:

Try to answer the questions I posed, one by one.
 
JeffKoch said:
Then if you don't try, you'll deserve to flunk. :smile:

Try to answer the questions I posed, one by one.

thanks anyways.
 
Do you have a textbook? Have you tried researching it on the web or in a library?
 

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