A wire of length $L$ carries current $I$ along x - axis. A magnetic field $\overrightarrow{\mathrm{B}}=\mathrm{B}_0(\hat{\mathrm{i}}-\hat{\mathrm{j}}-\hat{\mathrm{k}}) \mathrm{T}$ acts on the wire. The magnitude of magnetic force acting on the wire is

A concave lens (refractive index $=1.5$ ) has both surfaces of same radius of curvature R . If it is immersed in a liquid of refractive index 1.75 it will act as a

When the pressure of the gas contained in a closed vessel is increased by $2.3 \%$, the temperature of the gas increases by 4 K . The initial temperature of the gas is

A ray of light from a monochromatic point source of light is incident at a point on the screen. If a thin mica film of thickness ' $t$ ' and refractive index ' $n$ ' is introduced in its path, then the optical path