In Young's double slit experiment, width of the second slit is double the width of first slit, consequently the amplitude of the light from two slits. '$I_m$' is the maximum intensity. The resultant intensity '$I$' when they interfere with the phase difference of $\phi$ is given by

In a single slit diffraction experiment, for wavelength '$\lambda$', half angular width of the principal maxima is '$\theta$'. Also for wavelength of light '$p\lambda$', the half angular width of the principal maxima is '$q\theta$'. The ratio of the half angular widths of the first secondary maxima in the first case to second case will be

Three identical polaroids $P_1$, $P_2$ and $P_3$ are placed one after another. The pass axis of $P_2$ and $P_3$ are inclined at angle of $60^\circ$ and $90^\circ$ with respect to axis of $P_1$. The source has an intensity $I_0$. The intensity of light finally coming out is

In Young's double slit experiment, two slits are illuminated with a light of wavelength $\lambda$. The line joining $A_1P$ is perpendicular to $A_1A_2$ as shown in figure. If the first minimum is detected at P, the value of slits separation 'a' will be
(D = distance between source and screen)