As we know, radiation is energy which is emitted by a source, then travels through a medium, such as air, until it is absorbed by matter. Based on the energy of the radiated particles, they are classified as follows:

Ionizing radiation is radiation with sufficient energy that produces ions in the matter at the molecular level upon the interaction. In other words,  it can remove tightly bound electrons from the orbit of an atom, causing the atom to become charged or ionized. If the interacting matter is a human body, it can result in significant damage including damage to DNA and denaturation of proteins. This is not to say that non-ionizing radiation can’t cause injury to humans but the injury is generally limited to thermal damage i.e. burns. One of the most interesting things is that the visible spectrum is essentially the divide between ionizing and non-ionizing radiation. This makes sense clinically when we think of UV radiation causing skin cancer.

Ionizing radiation is caused due to unstable atoms that either has excess energy or mass or both. In order for them to get back to a stable state, they have to release the extra mass or energy in the form of radiation. Given below are the different types of ionizing radiation along with a few of their characteristics:

1. Alpha particles
2. Beta particles
3. Gamma rays
4. X-rays

## What are Alpha Particles?

The particles consisting of two protons and two neutrons that are bound together are known as alpha particles. These particles are identical to the helium atom and are emitted during radioactive decay and are known as alpha decay.

### Uses of alpha particles

• They are used as smoke detectors. When the smoke enters the detectors, the number of alpha particles reduce and get detected by the alarm. Americium-241 is an example of a smoke detector.
• They are used as static eliminators to remove the static charges from the equipment. Polonium-210 is an example of static eliminator.

## What are Beta particles?

Particles that are having high energy electrons or positrons are known as beta particles. These are ejected during the radioactive decay and are known as beta decay.

### Uses of beta particles

• Strontium-90 is used for the treatment of bone cancer.
• For emergency lighting, tritium is used.

## What are Gamma Rays?

During radioactive decay, a packet of electromagnetic energy is emitted by the nucleus known as a gamma ray. In the electromagnetic spectrum, gamma photons are the most energetic photons.

### Uses of gamma rays

• Cobalt-60 is used for sterilization of medical equipment and pasteurisation of food.
• Caesium-137 is used for the measurement of soil moisture density and to measure and control the flow of liquids in industries.

## What are X-Rays?

X-ray is a packet of a photon that is produced by electrons that are external to the nucleus. They originate from the electron cloud of an atom.

#### Properties of X-rays

 Physical They are invisible to eyes but have the property of attenuation, absorption and scattering Chemical They produce highly active radical of OH ions that can bring chemical changes in the solution Biological They are used for cancer treatment and may cause genetic changes Physiochemical They are used for producing photographic films

### Uses of X-rays

• X-rays are used for crystallography and fluoroscopy to control the quality of materials.
• X-rays are used to detect tumours and infections.

The table given below lists the properties of Ionizing radiation.

 Properties of Ionising Radiation Type of Ionising Radiation Alpha particles Beta particles Gamma rays Nature Positively charged particles Negatively charged particles Uncharged electromagnetic radiation Charge +2e -e 0 Mass 6.6466*10-27kg 9.109*10-31kg 0 Natural Source $U_{236}^{92}$ $Co_{68}^{29}$ Excited nuclei formed due to alpha and beta decay

Non-ionizing radiation is the term given to radiation that has insufficient energy to cause ionization. These kinds of radiations contradict with ionizing radiation like x-rays, gamma rays, and alpha particles, which are on the other end of the spectrum and are unstable and reactive. Non-ionizing radiation can produce heat, which is how food is cooked in a microwave oven. Humans and other organisms can see some types of non-ionizing radiation, such as visible light and infrared light. Following are the types of non-ionizing radiation:

• Visible light
• Infrared
• Microwave
• Very Low Frequency (VLF)
• Extremely Low Frequency (ELF)

Sunlight is the main source of ultraviolet (UV) radiation. Prolonged exposure of skin to this radiation leads to skin cancers. Sun lamps and tanning beds also emit UV rays. It has a wavelength of 400 nm.

Following are the types of UV radiation:

• UVA
• UVB
• UVC

## What is visible light?

Visible light is defined as the electromagnetic spectrum that is visible to the human eye. When the full spectrum passes through the prism, the spectrum separates depending on their wavelength into the colours of the rainbow. The shortest wavelength (380 nm) is of violet and the longest wavelength (700 nm) is of red.

Infrared radiation (IR) is also known as infrared with the wavelength range 700 nm to 1 mm. These are longer than the visible light. Near wavelength, mid-wavelength, long-wavelength and far-infrared are the different categories of infrared.

### Uses of infrared waves

Following are the uses of infrared waves:

• Thermography is a method to determine the relative temperature of the object and for this infrared waves are used.
• Infrared waves are invisible but can be sensed as they conduct heat. Because of this property, infrared waves are used in physical therapy for heating purposes.

## What are microwaves?

Microwaves are waves with different wavelengths and frequencies. They have a wavelength of 30 cm to 1 mm and frequency between 300 MHz and 300 GHz.

Radio waves are the electromagnetic radiation that has a wavelength longer than infrared and travel at a speed of light. The propagation characteristics of the radio waves have different frequencies like long waves to cover the earth and short waves that get reflected off in the ionosphere.