Electromagnetic Waves

This is a multiple choice answer as classified in NCERT Exemplar

(c) From a diode antenna, the electromagnetic waves are radiated outwards.The amplitude of electric field vector Eo which transports significant energy from the source falls off intensity inversely as the distance from the antenna, i.e. 1/r

This is a multiple choice answer as classified in NCERT Exemplar

(c) As from the relation that electric and magnetic energy density are equal to one another so there ratio will be always 1:1

This is a multiple choice answer as classified in NCERT Exemplar

(d) The direction of propagation of electromagnetic wave is perpendicular to both electric field vector E and magnetic field vector B, i.e., in the direction of E*B .

This can be seen by the diagram given below

This is a multiple choice answer as classified in NCERT Exemplar

(c) E $\propto \text{exception 25:}$

$\frac{\left(E_1\right)}{\left(E_2\right)}$ = $\sqrt[]{\frac{P_1}{P_2}}$ = $\sqrt[]{\frac{1000}{50}}$

$E$ 2= E/ $\text{exception 25:}$

This is a multiple choice answer as classified in NCERT Exemplar

(b) as we know momentum = energy transferred/speed of light

= $\frac{20*30*30*60}{3*{10}^8}$ = 36 $*$ 10^-4kgms^-1

Momentum of reflected light =0

So momentum delivered is = 36 $*$ 10^-4kgms^-1

This is a multiple choice answer as classified in NCERT Exemplar

(b) the electromagnetic wave is 

E_r = E_oicos (kz-wt)

And reflected wave is given by

E_r = -E₀ (-i)cos (k (-z)+wt+ $\pi$ )

This is a multiple choice answer as classified in NCERT Exemplar

(c) E=hv

V= $\frac{11*1.6*{10}^{-19}}{6.62*{10}^{-34}}$ = 2.65 $*$  10¹⁵hz this belongs to uv region

This is a short answer type question as classified in NCERT Exemplar

Since, electric field of an EM wave is an oscillating field and so is the electric force caused by it on a charged particle. This electric force averaged over an integral number of cycles is zero, since its direction changes every half cycle.

Hence, electric field is not responsible for radiation pressure.

This is a short answer type question as classified in NCERT Exemplar

As the distance is doubled, the area of spherical region ( 4πr² )

will become four times, so the intensity becomes one fourth the initial value but in case of laser it does not spread, so its intensity remain same.

Geometrical characteristic of LASER beam which is responsible for the constant intensity are as following

(i) Unidirectional

(ii) Monochromatic

(iii) Coherent light

(iv) Highly collimated

These characteristic are missing in the case of light from the bulb.

This is a short answer type question as classified in NCERT Exemplar

Pressure = force/area

Force =dp/dt

U=p.C or p= U/c

Pressure = $\frac{1}{A}.\frac{U}{C.dt}$

Pressure = I/C