A broad sources of light of wavelength `680nm` illuminated normally two glass plates.`120nm`long that meet at one end and are separated by a wire`0.048 mm`in diameter at the other end,Find the number of bright fringes formed over the `120nm`distance.

Options

A. 50
B. 100
C. 200
D. 400

Answer

B

Explanation

Constructive interence happens when
`2t=(m-1//2)lamda`. The minimum value for m = is m = 1,
the maximum value is the integer portion of
`(2d)/lamda+1/2=(2xx0.034xx10^(-3))/(680xx10^(-9))+1/2=100.5`
`m_(max)=100`