Wave Optics335Thus, ()2222122tansin1sin2cossincosntntnt2δθθθ=−=The condition for constructive interference is then ( )22cos12ntmλ=+=−(b) When 130.0=, then °( )1121.00 sin30.0sinsin21.21.38n−−°==0msinn=°For minimum thickness, =which gives a thickness of ( )201259115 nm2 cos4 1.3821.2tn+=°0 nmcos24.70The indirect ray suffers a phase reversal as it reflects from the mirror, but there is no reversal for the direct ray. Therefore, the condition for constructive interference, with the two sources separated by distance 2d, is 12sin2
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