Ami to main a join korum oitate na tor kototuko kopano shesh math practice suru korum theory dekhse but mone thaktase na math practice suru korum theory dekhse but mone thaktase na amio math dekhum ekhon r kale tr copy marum r kale tr copy marum dekha jaibo ne sob to paros e ki copy korbi vondo interference fringes are formed by a biprism whose acute angle is 20' and refractive index is 1.5. The slit is 10cm from the biprism and is illuminated by light of wavelength 6k Angstrom find the fringe width on a screen placed at a distance of 1 metre from the biprism

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.