Speed of electromagnetic wave in a medium having relative permittivity $$\varepsilon_r$$ and relative permeability $$\mu_r$$ is (speed of light in air, $$c=3\times10^8$$ m/s)

A 30 mW laser beam has a cross-sectional area of 15 mm². The magnitude of the maximum electric field in this electromagnetic wave is given by

[Permuittivity of space, $$\varepsilon_0=9\times10^{-12}$$

Speed of light, $$c=3\times10^8$$ m/s]

The correct arrangement in increasing order of wavelength of X-rays, UV rays, microwave is

Which of the following waves are used to treatment of muscles ache?