Two wave-fronts are emitted from coherent sources of path difference between them is $2.1$ micron. Phase difference between the wave-fronts at that point is $7.692\ \pi$. Wavelength of light emitted by sources will be :
A screen is at a distance of $1\ m$ away from the aperture. If light of wavelength $500\ nm$ falls on an aperture, then area of first HPZ and radius of third HPZ are :
The sodium yellow doublet has wavelengths $5890\mathring{A}$ and $'\lambda' \mathring{A}$ and resolving power of a grating to resolve these lines is $982$, then value of $\lambda$ is :
The phenomenon of diffraction can be treated as interference phenomenon if the number of coherent sources is
In Fresnel's biprism expt., a mica sheet of refractive index 1.5 and thickness 6 $\times$ 10$^{-6}$m is placed in the path of one of interfering beams as a result of which the central fringe gets shifted through 5 fringe widths. The wavelength of light used is
An aperture of size a is illuminated by a parallel beam of light of wavelength $\lambda$. The distance at which ray optics has a good approximation is
Diffraction gratings provide much brighter interference pattern since more light passes through them compared with double slits.
In biprism experiment, the distance of 20th bright band from the centre of the interference pattern is 8 mm. The distance of the 30th bright band is
In a biprism experiment, the fringe width obtained on the screen is $6\ mm$ from the slits which are $1.5\ m$ away from each other. Keeping the setting unchanged if the eye-piece is moved $20\ cm$ towards the biprism, find the change in fringe width.
In a Fresnel's bi-prism experiment, the fringe of width $0.05mm$ is observed on a screen at a distance of $1.5m$ from the source . When a convex lens is placed between the source and the screen, for two positions of the lens image of interfering sources are produced on the screen. The separation between the two images being $0.04$ and $0.01mm$, respectively. The wavelength of light used is