A 550 lines/mm diffraction grating is illuminated by light of wavelength 500 nm . Part A How many bright fringes are seen on a 3.8-m-wide screen located 2.2 m behind the grating?

7bright fringes

Explanation:

First we know that

Sinစ m,max= Mmax, x lambda/d

To find Mmax

Sin90° = Mmax x lambda/d = 1

So

Mmax= d/ lambda

= lambda= 500nm

d= 1/550mm

So

= 1.8 x10-6/500x 10^-9m

= 3.6

So m is approx 3

So 3 bright fringes above below and the central bright fringe itself making 7bright fringes

car a and b are moving in opposite directions

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