A plane electromagnetic wave propagating in $\mathrm{x}$-direction is described by

$\mathrm{E}_{\mathrm{y}}=\left(200\  \mathrm{Vm}^{-1}\right) \sin \left[1.5 \times 10^7 \mathrm{t}-0.05\  \mathrm{x}\right] \text {; }$

The intensity of the wave is :(Use $\epsilon_0=8.85 \times 10^{-12} \mathrm{C}^2 \mathrm{~N}^{-1} \mathrm{~m}^{-2}$ )

Two electrons are moving with same speed $v$. One electron enters a region of uniform electric field while the other enters a region of uniform magnetic field. Then after some time if the de-broglie wavelength of the two are ${\lambda _1}$ and ${\lambda _2}$  then

A laser beam can be focussed on an area equal to the square of its wavelength A $He-Ne$  laser radiates energy at the rate of $1\,mW$ and its wavelength is $632.8 \,nm$. The intensity of focussed beam will be

Give equation which relate $c,{\mu _0},{ \in _0}$.

The ratio of average electric energy density and total average energy density of electromagnetic wave is:

What physical quantity is the same for $X-$rays of wavelength $10^{-10} \;m ,$ $red$ light of wavelength $6800\; \mathring A$ and radiowaves of wavelength $500 \;m ?$