To radiate EM signal of wavelength $$\lambda$$ with high efficiency, the antennas should have a minimum size equal to:

A vehicle of mass $$200 \mathrm{~kg}$$ is moving along a levelled curved road of radius $$70 \mathrm{~m}$$ with angular velocity of $$0.2 ~\mathrm{rad} / \mathrm{s}$$. The centripetal force acting on the vehicle is:

Two planets A and B of radii $$\mathrm{R}$$ and 1.5 R have densities $$\rho$$ and $$\rho / 2$$ respectively. The ratio of acceleration due to gravity at the surface of $$\mathrm{B}$$ to $$\mathrm{A}$$ is:

In an electromagnetic wave, at an instant and at particular position, the electric field is along the negative $$z$$-axis and magnetic field is along the positive $$x$$-axis. Then the direction of propagation of electromagnetic wave is: