Light of wavelength 650 nm is incident normally upon a glass plate. The glass pl

Question

Light of wavelength 650 nm is incident normally upon a glass plate. The glass plate rests on top of a second plate so that they touch at one end and are separated by 0.0325 mm at the other end as shown in the figure.

Which range of values contains the horizontal separation between adjacent bright fringes?

a.

5.6 mm to 7.0 mm

b.

1.4 mm to 2.8 mm

c.

4.2 mm to 5.6 mm

d.

1.1 mm to 1.4 mm

e.

2.8 mm to 4.2 mm

a.

5.6 mm to 7.0 mm

b.

1.4 mm to 2.8 mm

c.

4.2 mm to 5.6 mm

d.

1.1 mm to 1.4 mm

e.

2.8 mm to 4.2 mm

Explanation / Answer

the condition for constructive inteference in a film ofthickness t and index of refractive index n surrounded by airis

2nt = (m + (1/2)) * ? (m =0,1,2,....................)

n = 1,m = 0 and ? = 650 nm

or ?1 = [2nt/(m + (1/2)]

similarly,

?2 =  [2nt/(m + (1/2)]

m = 1

therefore,the range of values for is ?1 to?2

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