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
Two guns P and Q can fire bullets at speeds 2 km/s and 4 km/s, respectively. From a point on a horizontal ground, they are fired in all possible directions. The ratio of maximum or areas covered by the bullets fired by the two guns, on the ground is