In Young’s double-slit experiment using monochromatic light of wavelength λ, the intensity of light at a point on the screen where path difference is λ, is K units. What is the intensity of light at a point where path difference is λ /3?
Let I1 and I2 be the intensity of the two light waves.
For monochromatic light waves, I1 = I2
If, Ø = Phase difference between the two waves
Then, their resultant intensities can be obtained by the relation:
Phase difference of the light is given by: 2¶/λ x Path Difference
When path difference = λ,
Phase difference, Ø = 2¶
∴ I' = 2I1 +2I1 = 4I1
Given, I’ = K
∴ I1 = K/4
When path difference = λ/3
Phase difference, ø = 2¶/3
Hence, resultant intensity is given by,
Using equation (1), we can write:
IR = I1 = K/4
Hence, the intensity of light with path difference of λ/3 is K/4 units.
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