(adsbygoogle = window.adsbygoogle || []).push({}); Please help me in this light problem!!!

HI!

well would u please help me in solving this problem the peoblem is:

"a laser beam of diameter 1cm is pointed on the moon. what is the diameter of the area illuminated on the moon. The moon is about 240000 miles away. take wavlength=6328A."

The solution that im using is this.

tan (lambda/2d)=x/2/R ; (R is the distance between the moon and the slit)

since lamda<<d

therefore tan (lambda/2d)=lambda/2d

so we now have:

lambda/2d=x/2R

or x=lamda(R)/d

where x is the required answer.

Now tell me that that is this the right method to get the required answer?

if not then what is the right method?

secondly can u explain how we can take angle as lamda/2d

Thanks in advance

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# Homework Help: Please help me in this light problem

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