Problem 5.74

The distances from a Fresnel biprism to a narrow slit and a screen are equal to \(a=25 \mathrm{~cm}\) and \(b=100 \mathrm{~cm}\) respectively. The refracting angle of the glass biprism is equal to \(\theta=20^{\prime}\). Find the wavelength of light if the width of the fringe on the screen is \(\Delta x=0.55 \mathrm{~mm}\).