# The Maximum Intensity Of Fringes In Young's Experiment Is I. If One Of The Slits Is Closed, Then Intensity At That Place Becomes I0. Then Relation Between I And I0 Is

Suppose slit width’s are equal, so they produce waves of equal intensity, say I’. Resultant intensity at any point.

$$I_{R} = 4{I}’cos^{2} \o$$ $$\o$$ is the phase difference between the waves at the observation point.

For maximum intensity,$$\o = 0^{\circ}$$ $$\Rightarrow I_{max} = 4{I}’ = I —[1]$$

If one of the slits is closed, the resultant intensity at the same point will be$${I}’$$only

$${I}’ = I_{0}—[2]$$

Now, comparing both the equations – [1] and [2], we get

$$I = 4I_{0}$$

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