Electromagnetic Waves and Spectrum

$\lambda = \frac{c}{f} = \frac{3 \times 10^8}{20 \times 10^9} = \frac{3}{200} \\ \text{Gain} \hspace{1cm} G_P = \eta \pi ^2(\frac{D}{\lambda})^2 = 0.7 \times \pi^2 \bigg(\frac{1}{\frac{3}{100}}\bigg)^2 = 30705.4 \\ = 44.87 dB$

Electromagnetic waves are arranged in order of increasing energy (or frequency): Radio waves (lowest energy), Microwaves, X-rays, and γ-rays (gamma rays, highest energy). The sequence 4 (radio), 3 (microwaves), 1 (X-rays), 2 (γ-rays) represents increasing energy levels. Energy is directly proportional to frequency (E = hf) and inversely proportional to wavelength.

Correct Answer: electro-magnetic waves of short wavelength

X-rays have wavelengths in the range of 0.1 to 10 nanometers, with 1 angstrom (0.1 nanometers) being a characteristic order of magnitude. This is much shorter than visible light (400-700 nm), allowing X-rays to penetrate materials. Options A, B, and D are orders of magnitude too large.

In vacuum, all electromagnetic waves travel at speed c (3×10^8 m/s) regardless of frequency or wavelength. Different types have different frequencies and wavelengths but identical speed in vacuum.

 Photosynthetically active radiation( PAR), designates the spectral range (wave band) of solar radiation from 400 to 700 nanometers that photosynthetic organisms are able to use in the process of photosynthesis. This spectral region corresponds more or less with the range of light visible to the human eye. Photons at shorter wavelengths tend to be so energetic that they can be damaging to cells and tissues, but are mostly filtered out by the ozone layer in the stratosphere. Photons at longer wavelengths do not carry enough energy to allow photosynthesis to take place.

Light year is the distance that light travels in vacuum in one year.

Terahertz radiations begin at a wavelength of one millimetre and proceed into shorter wavelengths.

This option is correct because X-rays and microwaves (in fact all electromagnetic waves) travel with velocity of light.

Ultraviolet (UV) light is an electromagnetic radiation with a wavelength from 400 nm to 10 nm, shorter than that of visible light, but longer than X-rays. Energy: 102 Electron Volts

Yes, this is correct, as both the statements are true.

It takes 0.1 µsec to transmit a bit at 10 Mbps rate. Thus, the bit lasts 0.1 µsec in time , during which it propagates 20 meters. Thus, a bit is 20 meters long here  as the speed of light in coax about is 200,000 km/sec (200 meters/µsec).

Wavelength is inversely proportional to the mass of the particle. The masses of these nuclei follow the order: electron>hydrogen>helium>neon