Given, amplitude of the magnetic field part of harmonic electromagnetic wave,
B₀ = 510 nT = 510 \(\times\)10^-9 T
Speed of light in a vacuum, c = 3 × 10⁸ m/s
Amplitude of electric field of the electromagnetic wave is given by the relation,
E = cB₀
= 3 × 10⁸ × 510 × 10⁻⁹ = 153 N/C
Therefore, the electric field part of the wave is 153 N/C.

\({ I }_{ D }={ \epsilon }_{ 0 }\frac { { d\phi }_{ E } }{ dt } ={ \epsilon }_{ 0 }\frac { EA }{ t } =\frac { { \epsilon }_{ 0 }(V/d)\times A }{ t }\)
\( =\frac { { \epsilon }_{ 0 }VA }{ td } =\frac { 8.85\times { 10 }^{ -12 }\times 400\times (60\times { 10 }^{ -4 } }{ } \)
\( =1.062\times { 10 }^{ -2 }\)

(a)  \(\lambda =\frac { c }{ v } =\frac { 3\times 10^{ 8 } }{ 2.0\times 10^{ 10 } } \)
\( =1.5\times 10^{ -2 }m\)
\(E=48Vm^{ -1 }\)
(b) \({ B }_{ 0 }=\frac { E_{ 0 } }{ c } =\frac { 48 }{ 3\times { 10 }^{ 8 } }\)
or  \({ B }_{ 0 }=1.6\times 10^{ -7 } \ T\)
(c) Energy density in E field, 
\({ U }_{ E }=\frac { 1 }{ 2 } \varepsilon _{ 0 }{ E }^{ 2 }\)
Energy density in B field, 
\({ U }_{ B }=\frac { 1 }{ 2\mu _{ 0 } } B^{ 2 }\)
Using \(E=cB\) and \(c=\frac { 1 }{ \sqrt { \mu _{ 0 }\varepsilon _{ 0 } } } ,\)
We find \({ U }_{ E }={ U }_{ B }\).

Total energy falling on the surface,
U = 18 x 20 x 30 x 60 J = 6.48 x 10⁵ J
Total momentum delivered to the surface is
\(p=\frac { U }{ c } =\frac { 6.48\times { 10 }^{ 5 } }{ 3\times { 10 }^{ 8 } } =2.16\times { 10 }^{ -3 }kg{ ms }^{ -1 }\)
The average force exerted on the surface is
\(F=\frac { p }{ t } =\frac { 2.16\times { 10 }^{ -3 } }{ 30\times 60 } =1.2\times { 10 }^{ -6 }N\)
It the surface is a perfect reflector, the change of momentum will be = p - (- p)
= 2 p = 2 x 2.16 x 10^-3 kg ms^-1
Now average force,
\(F=\frac { 2\times 2.16\times { 10 }^{ -3 } }{ 30\times 60 } =2.4\times { 10 }^{ -6 }N\)

Consider an electric charge at rest so that at a point P some distance away, we have electric field but no magnetic field. Let, at time \(t=0\) , an impulse be given to the charge such that it starts moving with some finite velocity. For a moving charge, we expect at P both electric and magnetic fields, but we cannot immediately decide whether the magnetic field at P will change from zero to finite value instantaneously at \(t=0\) or after some time.
Instantaneous change means infinite rate of change. If the change is instantaneous at all points then considering any loop, we will conclude from Faraday's law that an infinite e.m.f. and infinite electric field is set up. This in turn would imply an infinite magnetic field as seen from the result. Fields are always finite away from charges and clearly the situation just described is inconsistent with known laws of electricity and magnetism.
\(\oint { \overset { \rightarrow }{ B } } .\overset { \rightarrow }{ dl } ={ \mu }_{ 0 }{ \varepsilon }_{ 0 }\frac { d\phi _{ e } }{ dt } \)
The moving charge sets up a magnetic field in its neighbourhood which in turn creates an electric field in the neighbourhood. The process continues since both time-varying electric and magnetic fields act as sources of each other. Thus an electromagnetic wave is started when a charge is accelerated. It is only when the wave reaches the point P that the magnetic field at P changes.
This shows that an accelerated charge emits an electromagnetic wave. It can also be shown that the electromagnetic wave and the oscillator will have the same frequency.

During charging or discharging of a capacitor. Increasing or decreasing current in a circuit with time flows due to conduction current in wire and displacement current between the plates of a capacitor. when capacitor get fully charged both conduction and displacement current becomes zero. That is why galvanometer shows a momentary. deflection at the time of charging or discharging.
The expression to explain this observation is \(\oint { \overset { \rightarrow }{ B } .\overset { \rightarrow }{ dt } } ={ \mu }_{ 0 }(I+{ I }_{ D })\)

Intensity of light is reduced to one fourth because the light beam spreads as it approaches into a spherical region of area \(4\pi { r }^{ 2 },i.e.,I\infty 1/{ r }^{ 2 }\) But laser beam does not spread, hence its intensity remains constant. Laser beam is unidirectional, monochromatic and coherent light, whereas the light from a bulb does not posses the above properties.

(i) \(2.21\times { 10 }^{ -12 }\quad J{ m }^{ -3 }\)
(ii) \(2.21\times { 10 }^{ -12 }\quad J{ m }^{ -3 }\)
(iii) \(4.42\times { 10 }^{ -12 }\quad J{ m }^{ -3 }\)
(iv) \(3.3\times { 10 }^{ -12 }\quad J{ m }^{ -3 }\)

oscillating electric and magnetic field of an electromagnetic wave are in the same phase