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Question
Two source S1 and S2 of intensity I1 and I2 are placed in front of a screen [Figure (a)]. The pattern of intensity distribution seen in the central portion is given by Figure (b).
 (a) |
 (b) |
- S1 and S2 have the same intensities.
- S1 and S2 have a constant phase difference.
- S1 and S2 have the same phase.
- S1 and S2 have the same wavelength.
Options
a, b and c
a, b and d
b, c and d
c and d
Solution
a, b and d
Explanation:
• For getting the sustained interference the initial phase difference between the interfering waves must remain constant, i.e., sources should be coherent.
For two coherent sources, the resultant intensity is given by `I = I_1 + I_2 + 2sqrt(I_1I_2) cos phi`
• Resultant intensity at the point of observation will be maximum
`I_("max") = I_1 + I_2 + 2sqrt(I_1I_2)`
`I_("max") = (sqrt(I_1) + sqrt(I_2))^2`
• Resultant intensity at the point of observation will be minimum
`I_("min") = I_1 + I_2 - 2sqrt(I_1I_2)`
`I_("min") = (sqrt(I_1) - sqrt(I_2))^2`
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