In biprims experiment, the $$4^{\text {th }}$$ dark band is formed opposite to one of the slits. The wavelength of light used is $$(\mathrm{d}=$$ distance between the slits, $$\mathrm{D}=$$ distance between scource and the screen)

In Young's double slit experiment using monochromatic light of wavelength '$$\lambda$$', the maximum intensity of light at a point on the screen is $$\mathrm{K}$$ units. The intensity of light at point where the path difference is $$\frac{\lambda}{3}$$ is

$$\left[\cos 60^{\circ}=\sin 30^{\circ}=\frac{1}{2}\right]$$

If two sources emit light waves of different amplitudes then

In Young's double slit experiment, the $$10^{\text {th }}$$ maximum of wavelength '$$\lambda_1$$' is at a distance of '$$Y_1$$' from the central maximum. When the wavelength of the source is changed to '$$\lambda_2$$', $$5^{th}$$ maximum is at a distance '$$Y_2$$' from the central maximum. The ratio $$\frac{Y_1}{Y_2}$$ is