The movement of electromagnetic wave without any physical contact of a body is called radiation. Example – light coming from the sun. Heat transfer form hoter to colder body.
All bodies radiate some energy except at zero Calvin. The energy emitted by the body is in the form of packets or quanta of energy called photon.
When the radiation is incident on the surface of a body some fractional part of energy is being absorbed by the surface, some fractional part of energy being transmitted by the surface and some fractional part being reflected by the surface.
The fractional part which is absorbed by the body is called absorbitivity of that body and it is denoted by sigma. The fractional part which is reflected by the body is called reflectivity and it is denoted by row. The fractional part which is transmitted by the body is called transmissivity and it is denoted by tow. Mathematical expressions for this
ρ + α + τ = 1
Where ρ is reflectivity, α is absorbitivity and τ is transmissivity.
The value of these are depend upon
1 nature of surface of the body
2 Temperature of the body. – greater the temperature greater will be the radiation
3 wavelength of the incident rays.
Black body
The body that absorbed all the radiation, and does not trasmite or reflect any radiation is called black body. i. e α =1 and ρ =τ=0. It doesn’t mean that for the black body the body should be black. For example snow which is white in colour and whose absorbitivity is 0.955 that is very near to the 1, hence it is a black body.
White body
The body which which reflects all the radiation is called white body. i.e α = τ = 0, ρ = 1.
Gray body
It is a hypothetical body because the value of absorbitivity, reflectivity and transmissivity does not varies with temperature. ρ + α + τ =1
It’s a term which instantly comes to our mind when we are blamed for overusing our mobiles and laptops or even sitting on the couch for innumerable hours, Radiation from any source is harmful to our physical and mental health and can have long term effects which can house many unwanted ailments.
The movement of energy in the form of waves through any medium/material is known as radiation, even though technology has turned the tables and offered various advantage and been a saviour at times, it can also be a slow killer. According to scientists its ionizing radiation which cause damage to skin, tissue, cells and DNA etc.
Be it mobile towers, laptops, microwaves, bombs, x-rays and even certain chemicals, long term exposure of these to these components can do collateral damage to humans, they all emit harmful radiation which can alter and damage our DNA and can also lead to cell mutation and other diseases. One of the most common examples is cancer.
One of the biggest devices which can harm humans is mobile towers or cellular towers, many people allow the companies to set up their cellular towers near their housing complex as the companies fund these people, they lure people by using money as a means to close their mouths, the rays from cellular towers can cause mutation of tissue cells and can damage tissue present inside our muscles. eventually in the long run it’s the people living near these towers who will be prone to worse case scenarios and will do harm to others as well. But many scientist claim this theory to be absolutely illogical and state that there are no harmful emissions from mobile towers.
When it comes to emission of these harmful bodies even the marine animals are greatly exposed to these radiation leading to death in huge number or even mutation.
X-ray machines also emit strong waves, long term exposure to x-ray machines and frequent exposure to these machines would lead to tumour formation and unwanted changes in the body whose effects can pass on to the next generation. The waves are smaller in size and are ionized and can lead to dismay.
Certain chemical emitted from factories through air ,gas or even water have shown eye opening and shocking changes when people were exposed to it, the absorbtion of these chemical through water, food or even air can lead to genetic mutation and these deadly changes can pass on for generations, carcinogens like benzene, beryllium, asbestos, vinyl chloride and arsenics.eg-many houses situated near factories especially in villages whose emissions are mixed in the air and water have become the source to numerous skin care diseases, disabilities, deformities and cancers.
One of the most devastating incident which left behind incurable wounds which have been passed on to the coming generations was the Bhopal Gas tragedy, One could literally notice the faults and imperfections in the new-borns of the victims of the gas tragedy, one eye missing, cleft lips or skin ailments. Such tragedies can hamper mental and physical growth and can also cause trauma which can become host to mental disorders like PTSD.
Radiation from nuclear explosions is also common especially in countries like Afghanisthan and Syria which all year around are bound by war between allies and enemies. The (35%) thermal, nuclear(15%) and blast(50%) energy produced from mighty explosions can cause severe damage along with the physical destruction it causes to its surroundings.
When it comes to emission of these harmful bodies even the marine animals are greatly exposed to these radiations leading to death in huge number or even mutation.
UVA and UVB rays from the sun can cause numerous ailments like cataract and skin cancer and do a huge amount of damage to the environment as well as the ozone layer. One of the main reason of coral bleaching in the great marine reef is the absorption of Ultra violet rays.
We can clearly see the radical changes which radiation has caused and we can do our bit by exposing ourselves less to these harmful objects.
Although microorganisms are beneficial and necessary for human well being, microbial activities have undesirable consequences such as food spoilage and disease. To minimize there destructive effects, it is essential to kill a wide variety of microorganisms or inhibit their growth.
Heat Heating is still one of the most popular ways to destroy microorganisms. Fire and boiling water have been used since the time of Greeks for sterilization and disinfection. Exposure to boiling water for 10 minutes is sufficient to kill or destroy vegetative cells and eukaryotic spores, but not enough to kill or destroy bacterial endospores, hence boiling does not sterilize but can be used for disinfection of drinking water and objects not harmed by water. This can be carried out within an autoclave. Hot and saturated steam enters a chamber and the desired temperature and pressure which is usually 121°C and 15 pounds is reached. At this temperature and pressure the steam destroy all vegetative cells and endospores. Moist heat is thought to kill so effectively by degrading nucleic acids and by denaturing enzymes and other essential proteins It may also disrupt cell membranes. Pasteurization is a process where many substances such as milk, are treated with controlled heating at temperatures well below boiling. There are two types of pasteurization- flash pasteurization or high temperature short term (HTST) pasteurization and the other method used is ultra high temperature (UHT) pasteurization. Dry heat sterilization can also be used on many objects in the absence of water. The items to be sterilized are placed in an oven at 160 to 170°C.
Low temperatures Another convenient method to inhibit the growth and reproduction of microorganisms is to use lower temperatures like freezing or refrigeration. Mostly this method of control is used in food microbiology. Freezing items at -20°C or lower stops microbial growth because of the absence of liquid water and the ice crystal destruction of cell membranes at this temperature. This method is also used for long term storage of microbial samples in the laboratory in the form of glycerol stocks. This method of control at low temperatures slows microbial growth and reproduction but does not half it completely. Fortunately most pathogens are mesophilic and do not grow well at low temperatures around 4°C. Thus, refrigeration is a good technique only for short-term storage of food and other items.
Filtration The filters simply remove the microbes instead of killing them. The material used mostly is glazed porcelain, asbestos or other similar materials. Membrane filters are also used and have replaced depth filters in recent times. These filters are used to remove most vegetative cells, but not viruses from solutions ranging in volume from 1 ml to many liters. The other way this method is used is in the laminar flow biological safety cabinet where the air is sterilized by filtration. These cabinets contain high efficiency particulate air(HEPA) filters.
Radiation The radiations like ultraviolet and ionizing can be used for sterilizing objects. UV radiation is used as a sterilizing agent only in a few specific situations like UV lamps are placed on the ceilings of room for in biological safety cabinet to sterilize air and other exposed surfaces. Commercial UV units are available for water treatment. Pathogens and microorganisms are destroyed when a thin layer of water is passed under the lamps (water purifiers). Ionizing radiation penetrates deep into objects and is an excellent sterilizing agent. It destroys bacterial endospores and vegetative cells of both prokaryotic and eukaryotic origin but not against viruses. Gamma radiation from a Cobalt 60 source is used in the cold sterilization of antibiotics, hormones and plastic disposable supplies such as syringes and petri dishes.
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