In a YDSE arrangement, two slits are $0.5 \mathrm{mm}$ apart and screen is $50 \mathrm{cm}$ away from slits. White light is incident on the slits and it is observed that at the position $1 \mathrm{mm}$ from central bright fringe, some wavelengths are missing. The missing wavelength can be

A monochromatic beam of light falls on YDSE apparatus at some angle $\left(\theta \right)$ as shown. A thin sheet of glass (R.I. $=\mu ,$ thickness $=t$ ) is inserted in front of the lower slit $S_2.$ Select the correct alternative

A cylindrical wave front $ABC$ centred at $O$ (symmetric about $BE$ ) is incident on slits $S_1, S_2.$ $B{S}_1=S_{1}O=8\lambda$ where $\lambda$ is wavelength of light used. A slab of thickness $t$ and refractive index $\frac{4}{3}$ is placed in front of one of the slits to obtain central maxima at point $D$ (symmetrically located with respect to slits). If $t$ is least, then

A ray of light of intensity $I_0$ is incident on a parallel glass slab at point $P$ as shown. It undergoes partial reflection and refraction. At each reflection $40\%$ of incident energy is reflected. The rays $PQ$ and $P\text{'}Q\text{'}$ undergo interference. If for constructive interference, intensity is $I_1$ and for destructive interference, intensity is $I_2,$ then