Two interfering waves are arriving at a point on a screen with a path difference of `120 lamda`. The path difference is `72 mu m`. The wavelength of light is ____________. Is the point dark or bright?

Options

A. 6000Å bright
B. 8640Å, bright
C. 8640Å, dark
D. 6000Å dark

Answer

A

Explanation

Path diff. `=120lambda` and `72 mu m, lambda=?`
Path diff. `=120 lambda=72 mu m`
`:.lambda=(72xx10^(-6))/(120)=6xx10^(-7) m`
`lambda=6000 A^(@)`
Since path differene is equal to integral multiple of wavelenghts the given point is bright.