If a source of power $4\ kW$ produces $10^{20}$ photons/second , the radiation belongs to a part of the spectrum called

A plane electromagnetic wave of wavelength $\lambda $ has an intensity $I.$  It is propagating along the positive $Y-$  direction. The allowed expressions for the electric and magnetic fields are given by

In an electromagnetic wave the energy density associated with magnetic field will be

The electric field of an electromagnetic wave in free space is given by $\vec E$$=10 cos (10^7t+kx)$$\hat j$ $volt/m $ where $t$ and $x$ are in seconds and metres respectively. It can be inferred that

$(1)$ the wavelength $\lambda$ is $188.4\, m.$

$(2)$ the wave number $k$ is $0.33\,\,  rad/m.$ 

$(4)$ the wave is propagating along  $+x$ direction. 

Which one of the following pairs of statements is correct ?

The magnetic field in a plane electromagnetic wave is $\mathrm{B}_y=\left(3.5 \times 10^{-7}\right) \sin \left(1.5 \times 10^3 \mathrm{x}+0.5\right.$ $\left.\times 10^{11} \mathrm{t}\right) \mathrm{T}$. The corresponding electric field will be

Assume a bulb of efficiency $2.5\%$ as a point source. The peak values of electric field produced by the radiation coming from a $100\, W$ bulb at a distance of $3\, m$ is respectively.....$V\,{m^{ - 1}}$