Every body at all time, at all temperatures emit radiation (except at T = 0), which fall in the infrared region.

Microwaves are used to cook food. Microwave oven is a domestic application of these waves.

All bodies above absolute zero temperature emit electromagnetic radiation. The wavelength of radiation emitted depends on the temperature of the body. Most of the radiation emitted by the human body is mainly at the wavelength of 12 micron. The wavelength of infrared radiation is between 0.75 to 1000 micron (1 micron = 10^-6 metres). Hence , the majority of radiation emitted by human bodies lie in the infrared region.

Frequency from 3 GHz to 30 GHz comes in range of Super High Frequency band.

In spectrum. Band spectra is the name given to groups of lines so closely spaced that each group appears to be a band, nitrogen spectrum. Band spectra, or molecular spectra, are produced by molecules radiating their rotational or vibrational energies

Red has maximum wavelength and frequency doesn't change while travelling through a medium. 

The wavelength of microwave is around 5 mm and wavelenght of visible around 500 nm

None of the given above are electromagnetic waves, thus none of them have the velocity of light.

The range of wavelength of visible light is approximately $400-800 nm$ with violet being at the lower end ($380-450 nm$) and red at the higher end ($620-750 nm$). 

The range of frequencies from red to violet is 430-790 THz.

The range of wavelength for red is $6200-7500$ $A^o$

The range of wavelengths for blue is $4500-4950$ $A^o$.

The formula for velocity, when given wavelength and the frequency of the wave, is written as: $v=f\lambda $.
In this formula, $f$ represents frequency, $v$ represents the velocity of the wave, and $\lambda $ represents the wavelength of the wave.  
Here, the frequency of the wave is $500 MHz = 500000000 Hz$  and the wavelength is $60 cm = 0.6 m$
Hence, the velocity of the wave is $3\times { 10 }^{ 8 }m/s$.

In the order of increasing wavelength, the waves are Gamma rays ($< 1 nm$), X-rays ($1-10 nm$), infrared rays ($700-{ 10 }^{ 5 }nm$), micro waves (${ 10 }^{ 5 }-{ 10 }^{ 8 }nm$), radio waves (${ >10 }^{ 8 }nm$).
Hence, the radiations of wavelength just longer than ${ 8\times 10 }^{ -7 }m$ is Infrared.

Fraunhofer spectral lines are also called line absorption spectra. They are a set of spectral lines. The lines were originally observed as dark features (absorption lines) in the optical spectrum of the Sun.

Generally, three types of radiation come from the sun to Earth, they are, ultraviolet radiation, visible light, and,  infrared radiation. Out of these three radiations, ultraviolet radiation is prevented by the ozone layer and visible light and high-frequency infrared radiation reach to earth, because they can pass through the atmosphere of the Earth.

The frequency of $\gamma-$ rays is more than that of X-rays.

Cosmic rays are coming from outer space, having high energy charged particles, like $\alpha$-particle, proton etc. 

Infrared radiations are used as a part of thermal therapy. Thermal therapy is widely used for increasing the extensibility of the collagen, to decrease the joint stiffness, to relieve the muscle spasms, to increase the flow of the blood.

$\beta$ -rays are streams of electron and cosmic rays are waves coming from space. So they are not electromagnetic waves.

All of the options are uses of UV Radiations. 

EM waves travel with the same speed in vacuum (or air) which is same as the speed of light ie. $\displaystyle 3\times { 10 }^{ 8 }m/s$

Sunlight is reffered as white light. It consist of seven colours,i.e VIBGYOR

Gamma Rays are most energetic Radiations. Since they have high penetrating power, they can cause fluorescence on fluorescent materials like ZnS.

Frequency of gamma rays is greater than $3 \times 10^{19} Hz$

Electromagnetic waves are transverse waves. The electromagnetic waves of entire wave length range do not require any material we drive for their propagation.

Radiowaves are used in-

EM waves exhibit the properties of reflection and refraction. In refraction, when an EM wave passes from one medium to the another, its direction to travel,speed and wavelength changes, but frequency remains unchanged.

EM waves are not deflected by electric and magnetic field. They exhibit the property of reflection and refraction.

Long exposure to ultraviolet radiations can cause health hazards like skin cancer.

Microwaves are used in the following applications:

Both , ultraviolet and light wave are electromagnetic waves , having the speed of light , but in electromagnetic frequency spectrum ultraviolet wave falls before light wave , in the decreasing order of frequency.It means frequency of UV waves is greater than light wave.

Since the speed of any types of wave in vacuum remains constant so all wave travel at the same speed. 

Infrared light has longer wavelengths and lower energy than visible light and cannot be seen with the human eye. Mosquitoes, vampire bats, bed bugs, and some snake and beetle species, however, can use portions of the infrared spectrum for vision. Sometimes humans can “see" infrared energy in the form of heat.

Radio waves are the least energetic waves among other waves. They have the lowest frequency and thus the largest wavelength. Due to this large wavelength character, the radio waves are used in data transmission purposes, since they are hard to interact with particles in the atmosphere.

Speed of all the electromagnetic waves is constant and is equal to speed of light  i.e  $c$

Electromagnetic spectrum of visible light :     $VIBGYOR$

The visible light contains 7 colours  :  Violet, indigo, Blue, Green, Yellow, Orange and Red.

When the electrons in the atom are excited, for example by being heated, the additional energy pushes the electrons to higher energy orbits. When the electrons fall back down and leave the excited state, energy is re-emitted in the form of a photon.

Electromagnetic waves travel with constant speed equal to that of light  i.e  $v =c= constant$

The color with the lowest frequency corresponds to the longest wavelength, which is orange in this case.

Order of wavelength from smallest to largest :

Given :    $\nu = 7.5 \times 10^{14}$  Hz

Decreasing order of wavelength :

Increasing order of wavelength :

Given, electromagnetic flux $=10^3\, Wm^{-2}$
The area of roof $A= 6\, m \times 30\, m$
$=180 \, m^2$
The total power incident on roof
$P=10^3 \times 180$
$=1.8\times 10^5 \, W$

MRI gives very detailed pictures of soft tissues like the brain

1 eV = (1.6 x 10^-19 coulomb) x (1 volt)

= 1.6 x 10^-19 joule

15 keV = 18 x 10^-16 J …..(a)

Given that photon energy = hf = 15 keV

hf = hc/lambda …… (b)

Now hc = (6.63 x 10^-34 J-sec) x (3 x 10^8 m/sec)

= 19.89 x 10^-28 J-m …..(c)

From (b), lambda = hc/15 keV and from (a) & (c)

Lambda = (19.89 x 10^-28 J-m)/(18 x 10^-16 J)

= 1.105 x 10^-12 m

= 0.01105 Angstrom, which is in the x-ray range

Yellow light is a combination of red and green light. A dress appears yellow if it reflects red and green light to our eyes. In order to reflect red and green light, these two primary colors of light must be present in the incident light.
So, blue colored filter allows only blue color and absorbs all the remaining colors.
Therefore, yellow colored dress appears black.

Infrared radiation extends from the nominal red edge of the visible spectrum at $700nm$ to $1mm$.

Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. ultrasound devices operate with frequencies from 20000 Hz up to several gigahertz.

$E = 21 eV = 21 \times 1.6 \times 10^{-19}$

During the welding process, the ultra-violet rays are produced which are not visible but have an intense effect on the eyes. Therefore, the welder makes use of the special glass to protect his eyes.

All electromagnetic waves travels at the same speed in vacuum i.e $3\times10^8$ m/s. Due to the absence of matter, there is no change in speed corresponding to wavelength. There is no absorption and re-emission of light in the absence of matter.

The formula for velocity, when given wavelength and the frequency of the wave, is written as: $v=f\lambda $.
In this formula, $f$ represents frequency, $V$ represents the velocity of the wave, and $\lambda $ represents the wavelength of the wave.  
Here, the frequency of the wave is $500 MHz = 500000000 Hz$  and the wavelength is $60 cm = 0.6 m$
Therefore, the velocity of the wave is $3\times { 10 }^{ 8 }m/s$.
This determined velocity is the velocity of the light in air. Hence, the medium through which the wave is travelling is air.

The electromagnetic spectrum consists of the full range of known electromagnetic waves, including gamma rays, X-rays, ultraviolet light, visible light, infrared light, microwaves, and radio waves. All of these are produced by various forms of oscillating charges or currents. Electromagnetic waves are transverse waves which travel at the speed of light and involve oscillating electric and magnetic fields at right angles to each other.
Hence, the speeds of these waves when they travel in vacuum is same as the speed of visible light, that is, $3\times { 10 }^{ 8 }m/s$. Therefore, the ratio of their speeds is $1:1$.

We know that, $E = hv = \dfrac{hc}{\lambda}$
Hence highest energetic rediation is whose wavelength is atleast i.e $ \lambda = 0.01 A^{\circ}$

$Answer:-$ B 

Earth's atmosphere is divided into different layers, out of which the ozone layer absorbs the X-rays and $\gamma$-rays whereas visible light and microwaves are the waves which are not absorbed by any layer of atmosphere.

If we observe the electromagnetic spectrum , we see that gamma rays has the highest frequency.

Photosynthetically Active Radiation $(PAR)$ Is the amount of light available for photosynthesis, which is light in the $400$ to $700$ nanometer wavelength range. PAR changes seasonally and varies depending on the latitude and time of day.

Electromagnetic waves do not include light belong to electromagnetic spectrum.

Frequency range of Y rays=${ n } _{ 1 }=>3\times { 10 }^{ 20 }㎐$

Sky wave propagation is that mode of wave propagation in which the radio waves emitted from the transmitting antenna reach the receiving antenna after reflection in the ionosphere.

Absorption spectrum is inversly proportional to the wavelength of the wave.

The transverse nature of electromagnetic radiation is demonstrated by polarisation experiment.