In Young's double slit experiment, the distance between the slits is 2 mm and the slits are 1 m away, from the screen. Two interference patterns can be obtained on the screen due to light of wavelength ' $\lambda_1$ ' and ' $\lambda_2$ ' respectively. The separation on the screen between the $3^{\text {rd }}$ order bright fringes on the two interference patterns is ( $\lambda_2=1.5 \lambda_1$ )

In Young's double slit experiment, at two points $P$ and $Q$ on screen, waves from slits $S_1$ and $S_2$ have a path difference of 0 and $\frac{\lambda}{4}$ respectively. The ratio of intensities at point $P$ to that at $Q$ will be $\left(\cos 0^{\circ}=1, \cos 45^{\circ}=\frac{1}{\sqrt{2}}\right)$

In a biprism experiment a steady interference pattern is observed on the screen using a light of wavelength $5000 \mathop {\rm{A}}\limits^{\rm{o}}$. Without disturbing the set up of the experiment, the source of light is replaced by a source of wavelength $6400 \mathop {\rm{A}}\limits^{\rm{o}}$.

The fringe width will

In a single slit diffraction experiment, slit of width ' $a$ ' is illuminated by light of wavelength ' $\lambda$ ' and the width of the central maxima in diffraction pattern is measured as ' $y$ '. When half of the slit is covered and illuminated by light of wavelength (1.5) $\lambda$, the width of the central maximum in diffraction pattern becomes