$Answer:-$ B

Infrared radiation play an important role in maintaining the earths warmth or average temperature through the greenhouse effect.

The microwaves are preferred in order to communicate with the artificial satellites which are orbiting the earth at a particular height from the surface of the earth. The microwaves are preferred because they can penetrate through the Earth's atmosphere very easily and reach the target satellite.

The phenomenon involved in the reflection of radiowaves by ionosphere is similar to total internal reflection of light in air during a mirage (angle of incidence gt critical angle). It is same as the formation of the rainbow because it also involves the process of total internal reflection.

Ozone is a molecule made of three oxygen atom or $O _3$. When ultraviolet light in the range $240nm$ and $320 nm$ strikes an ozone molecule, it absorbs the energy and the $O _3$ changes to $O _2$ and $O$. The $O$ atom soon combines with another $O _2$ molecule to form $O _3$ and is ready to absorb ultra violet light.

The heating property of Infra red waves is used in solar heater and solar cells, Hence option (b) is correct. 

Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum. The electromagnetic waves can be produced using oscillator.

Herschel was testing filters for the sun so he could observe sun spots. When using a red filter he found there was a lot of heat produced. Herschel discovered infrared radiation in sunlight by passing it through a prism and holding a thermometer just beyond the red end of the visible spectrum.This thermometer was meant to be a control to measure the ambient air temperature in the room. He was shocked when it showed a higher temperature than the visible spectrum. Further experimentation led to Herschel's conclusion that there must be an invisible form of light beyond the visible spectrum.

$\alpha -ray$ is the sub atomic particles and their associated energy that are released during the decomposition of the unstable nuclei are referred to as radiation-

visible light, infrared and ultraviolet radiation cannot be used for communication.

Infrared waves are generally used to transmit information from remote controls.

Visible light is generally used for photography

Microwaves are used to transmit satellite television and for mobile phones.

Electromagnetic radiation is classified into types according to the frequency of the wave. These types include, in order of increasing frequency, radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.
The frequency is the inverse of wavelength. Hence, in the order of increasing wavelength, the waves are Gamma rays ($<1nm$), X-rays ($1-{ 10 }nm$), infra red rays ($700-{ 10 }^{ 5 }nm$), micro waves (${ 10 }^{ 5 }-{ 10 }^{ 8 }nm$), radio waves (${ >10 }^{ 8 }nm$).
Therefore, gamma rays has a wavelength of $0.01 \mathring{A}$.

The electromagnetic wave which helps in the study of structure of crystals is X-rays.
If a beam of x rays is passed through a crystal, it makes a pattern on a photographic plate. The pattern is called crystallogram (the arrangement of the atoms each crystal has its own crystallogram). It reveals the crystal`s internal structure. 

Electromagnetic radiation is classified into types according to the frequency of the wave. These types include, in order of increasing frequency, radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.
The frequency is the inverse of wavelength. Hence, in the order of increasing wavelength, the waves are Gamma rays ($<1nm$), X-rays ($1-10nm$), infra red rays ($700-{ 10 }^{ 5 }nm$), micro waves (${ 10 }^{ 5 }-{ 10 }^{ 8 }nm$), radio waves (${ >10 }^{ 8 }nm$).
Therefore, X-rays has a wavelength of $50 \mathring{A}$.

Microwaves are a form of electromagnetic radiation with wavelengths ranging from as long as one meter to as short as one millimeter; with frequencies between 300 MHz (0.3 GHz) and 300 GHz. This broad definition includes both UHF and EHF (millimeter waves), and various sources use different boundaries. 
Microwave technology is extensively used for point-to-point telecommunications (i.e. non-broadcast uses). Microwaves are especially suitable for this use since they are more easily focused into narrower beams than radio waves, allowing frequency reuse; their comparatively higher frequencies allow broad bandwidth and high data transmission rates, and antenna sizes are smaller than at lower frequencies because antenna size is inversely proportional to transmitted frequency. Microwaves are used in spacecraft communication, and much of the world's data, TV, and telephone communications are transmitted long distances by microwaves between ground stations and communications satellites.

X-rays is a form of electromagnetic radiation. Most X-rays have a wavelength ranging from $0.01$ to $10$ nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz (${ { 3\times 10 }^{ 16 }\ Hz\ to\ 3\times 10 }^{ 19 }Hz$) and energies in the range 100 eV to 100 keV.
Hence, the rays or waves of $0.1 nm$ is X-rays.

Johann Ritter decided to place silver chloride in the area just beyond the violet end of the spectrum, in a region where no sunlight was visible. To his amazement, he saw that the silver chloride displayed an intense reaction well beyond the violet end of the spectrum, where no visible light could be seen. This showed for the first time that an invisible form of light existed beyond the violet end of the spectrum. This new type of light, which Ritter called Chemical Rays, later became known as ultraviolet light or ultraviolet radiation (the word ultra means beyond).
Hence, the radiation which can be detected by a solution of silver chloride is Ultraviolet radiation.

Gamma rays are the most energetic light waves found on the electromagnetic spectrum.

Point contact diodes, commonly called crystals, are the oldest microwave semiconductor devices. Unlike the pn-junction diode, the point-contact diode depends on the pressure of contact between a point and a semiconductor crystal for its operation.One section of the diode consists of a small rectangular crystal of n-type silicon. A fine beryllium-copper, bronze-phosphor, or tungsten wire presses against the crystal and forms the other part of the diode During the manufacture of the point contact diode, a relatively large current is passed from the the wire to the silicon crystal. The result of this large current is the formation of a small region of p-type material around the crystal in the vicinity of the point contact. Thus, a pn-junction is formed which behaves in the same way as a normal pn-junction. The pointed wire is used instead of a flat metal plate to produce a high-intensity electric field at the point contact without using a large external source voltage.

Magnetic resonance imaging (MRI) is a technique that uses a magnetic field and radio waves to create detailed images of the organs and tissues within your body.

Most MRI machines are large, tube-shaped magnets. When you lie inside an MRI machine, the magnetic field temporarily realigns hydrogen atoms in your body. Radio waves cause these aligned atoms to produce very faint signals, which are used to create cross-sectional MRI images like slices in a loaf of bread.

The frequency of television signal is smaller than that of microwave and visible waves.

$Answer:-$ A option

$Answer:-$ C and D option

The tubelight has coating of fluorescent material which converts ultra violet light into visible light. Hence the light is more intense. 

$Answer:-$ A

Answer is A.

Astronauts communicate with each other in space when they are spacewalking through the use of radio waves. Radio wave signal are sent to their headsets which then translates the signal into the form of sound . When receiving and sending message to earth it is sent in the form of radio waves which is then translated to sound wave (message) by a radio set. 

Molecular spectra due to vibrational motion lie in the microwave region of electromagentic spectrum. Due to Kirchhoff's law in spectroscopy the same will be absorbed.

X-rays are useful in studying the structures of crystals

Answer is C.

The D region is the lowest of the regions within the ionosphere that affects radio communications signals to any degree. It is present at altitudes between about 60 and 90 kilometers and the radiation within it is only present during the day to an extent that affects radio waves noticeably. It is sustained by the radiation from the Sun and levels of ionization fall rapidly at dusk when the source of radiation is removed. It mainly has the affect of absorbing or attenuating radio communications signals particularly in the LF and MF portions of the radio spectrum, its affect reducing with frequency. At night it has little effect on most radio communications signals although there is still a sufficient level of ionization for it to refract VLF signals.
Hence, radio reception improve slightly during the night because, sunlight affects radio broadcasts to some extent during the day.

Infrared radiation was discovered in $1800$ by $William Herschel$.

Order of wavelength from shortest to longest :      

Wrong

Microwaves or short radiowaves are suitable for radar systems used in aircraft navigation because of their short wavelengths.

Ultraviolet rays (or waves) tan our skin and cause some substances to become fluoroseun sun is important source of ultraviolet light. Sun rays reach our skin and burns the upper layer of skin, causing sunburns prolonged doses of UV radiation can induce skin cancer in human beings.

In photocell cesium, coated oxidised silver cathode emits electrons for infrared light.

To distinguish between real gems and artificial gems a merchant may use infrared radiations. A number of synthetic gems can be distinguished from their natural counterparts by differences in their infrared spectra.  

Increasing order of wavelengths as given below
$\gamma-rays < X-rays >$ ultravoilet rays
Frequency order
$\gamma-ray > X-rays >$ ultravoilet rays
$\Rightarrow q > p > r$
Thus, $q > p$
$q > r$
$p > r$.

$A, C, D$

The magnetic field in a plane of electromagnetic  wave is given by

$X-$rays aren't deflected by electrons and magnetic fields because $x-$rays do not carry and charge. They are electro-magnetic radiations and therefore cannot be deflected by electronic or any magnetic fields.

Both assertion and reason are false.

Optical communication is always preferred over microwave

communication also Bandwidth and number of channels are more in case of optical communication.

$4\times { 10 }^{ 3 }={ 10 }^{ 20 }\times h\nu$ 

X-rays has a wavelength of $50 \mathring{A}$.
X-rays are used by doctors to see inside people. The machines are managed by a trained x-ray technician. They pass easily through soft tissues, but not so easily through bones.
Hence, they help in detecting fractures in bones.

The range of wavelength for visible light lies between, ${ 400 \ nm }<\lambda <{ 700 \ nm }$.

Photographers use film that is sensitive to infrared rays to take pictures in places where there is no visible light. 
IR light is longer in wavelength than visible light and focuses differently. Regular photographic lenses are made for visible light photography without any regard to what happens when photographing out of band light like IR. Therefore each lens design and focal length, even each focal length within a zoom lens will focus IR light differently.
Hence, infrared light is used for taking pictures in the dark.

Gamma rays are classically produced by the decay of atomic nuclei as they transition from a high energy state to a lower state known as gamma decay, but may also be produced by other processes. Paul Villard, a French chemist and physicist, discovered gamma radiation in $1900$, while studying radiation emitted from radium. Villard's radiation was named "gamma rays" by Ernest Rutherford in $1903$.
Hence,  the rays or waves produced by the changes in the nucleus of an atom is Gamma rays.

X-rays has a wavelength of $50\ A^o$.
All electromagnetic radiation, of which radio waves and X-rays are examples, travels at the velocity of light, in a vacuum. The only difference between the two is that the frequency of X-rays is very much higher than radio waves.
Hence, X-rays travels at a speed of ${ 3\times 10 }^{ 8 }m/s$.

Ozone layer also called ozonosphere contains relatively high concentrations of ozone ($O _{3}$) molecules. Approximately 90% of atmospheric ozone occurs in stratosphere, the region extending from 10 - 18 km to 50 km above the earth's surface. The ozone layer effectively blocks certain types of ultraviolet and other forms of radiations that could injure or kill most living things.

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

Visible light means i.e visible to human eye.

wavelength of following lights are:
$\gamma$-rays:$10pm$
x-rays:($10pm-10nm$)
UV-rays:($10nm-380nm$)
visible rays:($380nm-750nm$)
so,visible rays has maximum wavelength.

We know that radiation is emission or transmission of energy in the form of waves or particles.

Infrared radiation are used in microwaves ovens in electronagnetiic spectrum frequency and energy of microwave is smaller than visible light water contain is required for coobing food in microwave oven almost all food item contain some water contain.Microwaves interact with water molecules all atoms via their electric and magnetic fileds. Temprature of water molecules increases by this these water molecule share this energy with neighbouring food molecules, heating up the food.

Hydrogen is the least energetic element. Even the most energetic line that hydrogen emits (when an electron drops down from the second shell to the first) has only enough energy to be an ultraviolet photon. This is because the energy levels in hydrogen atom are very close. So hydrogen atoms do not emit X rays.

X-rays are produced by bombarding a metal target with high energy electrons.

Frequency of Radio waves = $<3\times { 10 }^{ 9 }$Hz

The working of microwave oven involves absorption of microwaves by matter.

$X$-Rays Wavelength range $=1\times { 10 }^{ -11 }m$ to $3\times { 10 }^{ -8 }m$
So,                          $=0.001 nm$ to $1 nm$

X-rays are electromagnetic waves with a wavelength less than about $10^{-9}$m. Cathode rays comprise of a beam of electrons. $\alpha$-rays are made up of helium nucleus(i.e., $^{4} _{2}He^{2+}$), hence are made up of positively charged particles, whereas $\beta$-rays are made up of energetic electrons, hence comprise of negatively charged particles.

International broadcasting requires high frequency radio waves which have high energy to travel over long distance.

As we know, $\boxed{E _{max}=\dfrac{hc}{\lambda _{min}}}$

Cobalt therapy or cobalt $60$ therapy is the medical use of gamma rays from the radio isotope cobalt $-60$ to treat conditions such as cancer. Thus, Cobalt $-60$ is the radio isotope useful in treating the blood cancer.

X-ray is an electromagnetic waves which moves with a speed equal to   $3\times 10^8 \ m/s$

For an electromagnetic radiation, only momentum is quantised$.$