The magnetic field of an electromagnetic wave is given by $\vec B = 1.6 \times 10^{-6} \cos(2 \times 10^7 z + 6 \times 10^{15} t) (2\hat i + \hat j) \text{ Wb/m}^2$. The associated electric field will be

Which one of the following statements is correct?

If the intensity of an electromagnetic wave is $0.02 \ W/m^2$ and its velocity in free space is $3 \times 10^8 \ m/s$,then the energy density of the radiation is ..... $J/m^3$.

Answer the following questions:
$(a)$ Long distance radio broadcasts use short-wave bands. Why?
$(b)$ It is necessary to use satellites for long distance $TV$ transmission. Why?
$(c)$ Optical and radio telescopes are built on the ground but $X$-ray astronomy is possible only from satellites orbiting the earth. Why?
$(d)$ The small ozone layer on top of the stratosphere is crucial for human survival. Why?
$(e)$ If the earth did not have an atmosphere,would its average surface temperature be higher or lower than what it is now?
$(f)$ Some scientists have predicted that a global nuclear war on the earth would be followed by a severe 'nuclear winter' with a devastating effect on life on earth. What might be the basis of this prediction?

All components of the electromagnetic spectrum in vacuum have the same

You are driving in your car listening to music on the radio. Your car is equipped with a radio that can receive radio signals of frequency $(f_1 \approx 3 \, MHz)$,$(f_2 \approx 30 \, MHz)$,and $(f_3 = 3 \, GHz)$. You enter a tunnel with a circular opening of diameter $10 \, m$. Which kind of radio signal will you be able to receive for the longest distance as you continue to travel in the tunnel?