A bar magnet of length $$6 \mathrm{~cm}$$, is placed in the magnetic meridian with $$N$$ pole, pointing towards the geographical north. Two neutral points, separated by a distance of $$8 \mathrm{~cm}$$ are obtained on the equitorial axis of the magnet. If $$B_H=1.2 \times 10^{-5} \mathrm{~T}$$. Then the pole strength of the magnet is
A force F applied on the wire of radius r and length L and change in the length of the wire is $$l$$. If the same force F is applied on the wire of the same material and radius 4r and length $$4l$$, then change in length of the other wire is,
A 30 mW laser beam has a cross-sectional area of 15 mm2. The magnitude of the maximum electric field in this electromagnetic wave is given by
[Permuittivity of space, $$\varepsilon_0=9\times10^{-12}$$
Speed of light, $$c=3\times10^8$$ m/s]
The average kinetic energy of a molecule in air at room temperature of 20$$^\circ$$C