Question

In a biprism experiment, a slit is illuminated by a light of wavelength 4800 Å The distance between the slit and biprism is 15 cm and the distance between the biprism and eyepiece is 85 cm. If the distance between virtual sources is 3 mm, determine the distance between 4th bright band on one side and 4th dark band on the other side of the central bright band.

Answer 1

λ = 4800 Å = 4.8 × 10⁻⁷m,

 d = 3 mm = 3 × 10⁻³m,

D = 15 + 85 = 100 cm = 1 m

Distance between 4th bright band on one side and 4^th dark band on the other side of the central
bright band, (X4 + X′4) = ?
For n^th bright band,

The distance between 4th bright band on one side and 4th dark band on the other side of the central bright band is 12 × 10⁻⁴ m.