For electron to pass undeflected, electric force on electron = magnetic force on electron
i.e. $$eB = evB$$
$$\eqalign{ & {\text{or}}\,\,v = \frac{E}{B}\,\, \cr & {\text{or}}\,\,v = \frac{{\left| E \right|}}{{\left| B \right|}} \cr} $$

All components of electromagnetic spectrum travel in vacuum with velocity $$3 \times {10^8}\,m/s.$$

For electromagnetic waves we know that,
$$\eqalign{ & \frac{E}{B} = c \cr & \therefore \frac{{9 \times {{10}^{ - 4}}}}{B} = 3 \times {10^8}\,m{s^{ - 1}} \cr & \Rightarrow B = 3 \times {10^{ - 12}}\,T \cr} $$

Microwave oven acts on the principle of giving vibrational energy to water molecules.

An electromagnetic wave is the wave composed of the oscillations of electric and magnetic fields in mutually perpendicular planes and these oscillations are perpendicular to the direction of propagation of wave.
The direction of propagation of electromagnetic wave is given by poynting vector
$$S = E \times H = \frac{{E \times B}}{{{\mu _0}}}$$
This is parallel to $$E \times B.$$

Light waves are electromagnetic waves.

$$\vec s = \frac{{{E^2}}}{{C{\mu _0}}} = 26.5\,W{m^{ - 2}}$$

Incident momentum, $$p = \frac{E}{c}$$
For perfectly reflecting surface with normal incidence
$$\eqalign{ & \Delta p = 2p = \frac{{2E}}{c}; \cr & F = \frac{{\Delta p}}{{\Delta t}} = \frac{{2E}}{{ct}}; \cr} $$

Given:
Amplitude of electric field,
$${E_0} = 4\,v/m$$
Absolute permitivity,
$${\varepsilon _0} = 8.8 \times {10^{ - 12}}{c^2}/N - {m^2}$$
Average energy density $${u_E} = ?$$
Applying formula,
Average energy density $${u_E} = \frac{1}{4}{\varepsilon _0}{E^2}$$
$$ \Rightarrow {u_E} = \frac{1}{4} \times 8.8 \times {10^{ - 12}} \times {\left( 4 \right)^2} = 35.2 \times {10^{ - 12}}J/{m^3}$$

The wavelength of infrared region is $$8 \times {10^{ - 5}}cm$$   to $$3 \times {10^{ - 3}}cm.$$   So maximum wavelength of infrared region
$$\eqalign{ & = 8 \times {10^{ - 5}}cm \cr & \approx {10^{ - 4}}cm. \cr} $$