To produce the phenomenon of interference,we require two sources that emit radiation of:

The wave nature of light can be determined by $......$.

Two light beams of intensities $4\,I$ and $9\,I$ interfere on a screen. The phase difference between these beams on the screen at point $A$ is $0$ and at point $B$ is $\pi$. The difference of resultant intensities,at the points $A$ and $B$,will be $....I$.

Path difference between two light waves at a point $P$ for constructive interference will be

The difference in the number of wavelengths, when yellow light propagates through air and vacuum columns of the same thickness, is $1$. The thickness of the air column is (Refractive index of air $\mu_a = 1.0003$, Wavelength of yellow light in vacuum $\lambda_0 = 6000 \text{ Å}$)

Two monochromatic coherent light beams $A$ and $B$ have intensities $L$ and $\frac{L}{4},$ respectively. If these beams are superposed, the maximum and minimum intensities will be