This website uses cookies to ensure you have the best experience.

Thermionic Emission And Radiation And Half Lifes

1735 words - 7 pages

Thermionic Emission and Radiation and Half-Lifes

For the write-up section of my coursework I went on a trip to the Kent
and Canterbury Hospital in order to look at the application of physics
within the field of medicine. I intend to spend time explaining two
physics principles which have uses in this scientific field, and
illustrate how they are used, either within the diagnosis or treatment
of a patient.

Two principles:

1. Thermionic emission.

Thermionic emission

Thermionic emission is a phenomenon by which electrons are emitted
from the surface of a metal or metal oxide. The flow of these
electrons can only occur when the thermal vibrational energy of the
matrix overcomes the electrostatic forces preventing the electrons
leaving the surface.

Thermionic emission is entirely reliant upon the 'sea of free
electrons'. This is the collective name given to the one or two
electrons per atom, in any metal, which are free to move around and
are not bound to the atom. The velocities of these free electrons
follow a statistical distribution, and occasionally an electron will
have enough velocity to overcome the electrostatic retaining forces.
The minimum amount of energy required for one of these electrons to
escape is called the work function. The work function varies within
different materials.

The process can occur at any temperature above absolute zero but it is
extremely inefficient, therefore when ever thermionic emission is
being used or tested the material is heated to a very high
temperature. Another method used in increasing the amount of
thermionic emission taking place is to coat the surface of the metal
with a metal oxide due to the fact that oxides lower the work
function; this is simply because the electrostatic retaining forces
within oxides are far lower than those in metals.

Thermionic emission is an incredibly important principle within
medical science because it can be used to create x-rays, for use in
x-ray machines. An x-ray is created when a fast moving electron, such
as those produced in thermionic emission, loses a considerable amount
of energy instantaneously.

In x-ray machines, thermionic emission occurs in vacuum tubes. There
is a cathode which is also a heating filament so as to allow high
temperatures but also to provide a large area from which thermionic
emission can occur. The filament emits electrons very effectively when
it is red-hot therefore it is supplied with a huge voltage (70KV) it
is this potential difference which causes the huge velocitieof the
electrons. Directly opposite this filament is an angled tungsten anode
which attracts the electrons and causes huge velocity, this anode then
instantaneously slows them down which as I stated above causes the
production of x-rays. The...

Find Another Essay On Thermionic Emission and Radiation and Half-Lifes

Cummins: A Company with Emission Solutions and Innovation

2346 words - 9 pages importance of improvements with respect to environmental standards, including emissions and increases in fuel economy. In 2002, Cummins Emissions Solutions was launched after the need was identified for an emission solution that would help engines meet future regulations. In 2006, Cummins pioneered a hybrid diesel-electric bus which reduced fuel consumption and greenhouse gasses by more than 30 percent and met emission levels set for 2010, four

Nuclear Radiation and Its Effects on People

1007 words - 5 pages Radiation is energy emitted from the nucleus of an unstable atom in the form of particles and wave. All matter is composed of atoms, which are the smallest part of an element that retains the characteristics of that element. The atom consists of two parts, the nucleus of the atom and the electron shell. Within the nucleus there are positively charged particles called protons and neutral particles which are called neutrons. Orbiting around the

Comparing Nothing's Changed and Half-Caste

1020 words - 4 pages Comparing Nothing's Changed and Half-Caste Half-Caste and Nothing's Changed are two poems that, despite having different subjects, are full of similarities. Both Half-Caste and Nothing's Changed express anger. Although, the object of their anger is different. The anger in Half-Caste is directed at language, or more specifically the use of one phrase while the anger in Nothing's Changed is towards a culture. In Half-Caste Caribbean

Harry Potter and the Half Blood Prince

1550 words - 6 pages her first five book where written J.K. Rowling started the sixth book in the Harry Potter series is called The Half Blood Prince. This book of the series was published in the UK, us and other English-speaking countries on the 16th of July 2005 and achieved record sales (Rowling). J.K Rowling’s sixth book in the series Harry Potter and The Half Blood Prince expertly uses imagery, characterization, and motifs. Imagery plays an enormous roll in

"Harry Potter and the Half Blood Prince"

530 words - 2 pages The much awaited book of 'Harry Potter and the Half Blood Prince' brought no disappointment to children and adults of the world alike. J.K Rowling set the world of magic alight in her first book of Harry Potter. A writer who can make magic appear on the pages of her book, she truly has inspired readers of all age groups that anything can be brought alive if written or said properly.The 6th Harry Potter book includes the same main characters

tow and a half feminist men

1609 words - 7 pages The television show Two a Half Men focuses on three self-centered family members, two uncles’ men and a kid in the middle of a divorce, who now lives part time with millionaire friend/uncle Walton. The trio consists of Walton who is the millionaire whom bought the beach house after Charlie passed away after having problems with the actual producers, Allan, Charlie’s original brother who now lives with Walton because he feels bad and Jake

Film Trailers for Shrek, High Heels and Low Lifes, and Knights Tale

1170 words - 5 pages Lifes and a Knights Tale’. I will be discussing the similarities between all 3 trailers, listing my favourite trailer and giving reasons and explanations. At the end I shall conclude my opinions and will sum up my findings and state the effectiveness of each of the trailers. Firstly I will be writing about ‘Shrek’. ‘Shrek’ is an animated comedy film about an ogre trying to get everyone out of his swamp. He goes to rescue a princess from a

Radiation and Its Uses, Specifically in South Africa

2077 words - 9 pages imaging, hybrid imaging and Single photon emission, computed tomography techniques are now in major cities in South Africa. The largest contributor to radiation exposure is the effects on Humans. More than half of South African cancer patient require some sort of Radiotherapy treatment. During tumour treatment Radiotherapy delivers a huge amount of cytotoxic doses of radiation to humans. The fastest growing source of radiation exposure and

Nuclear Radiation: Effects, Facts And How We Can Stop It

538 words - 3 pages called "ionizing" radiation, which has the ability to take an electron from an atom. This is important because it is something that is happening all around the world, not just in one place. This problem is quite big. There is usually a nuclear power plant in most countries, which has the power to have a meltdown, and cause nuclear radiation. Also, most countries are surrounded by natural sources such as rocks, which can produce radium. Radium decay

Waste, Radiation, and Danger; The Hanford Nuclear Power Plants

1092 words - 4 pages Waste, Radiation, and Danger; The Hanford Nuclear Power PlantsAre nuclear power plants dangerous? In a word, yes, and Hanford is one of the oldest ones around, producing radiation since 1944. Radioactive materials emitted from a nuclear power plant, such as Hanford, can injure living tissue, and a high enough dose can kill. The public has seen the danger, although over a decade ago, the meltdown at Chernobyl will not be forgotten, and cannot

Ways of Transmitting Heat: Conduction, Convection and Radiation

1570 words - 6 pages Conduction, convection and radiation are the three methods through which heat can be transferred from one place to another. The (www.hyperphysics.com) first method is the conduction through which heat can be transferred from one object to another object. This process is defined as the heat is transmitted from one to another by the interaction of the atoms and the molecules. The atoms and the molecules of the body are physically attached to

Similar Essays

1187 words - 5 pages For decades, the effects of radiation has been studied by doctors around the world. X-rays are used in the medical and dental field to take radiographs of certain parts of a person's body. Some have become concerned of the long term and short term effects of having x-rays taken because of the radiation that is exposed. Since the rise of concern, studies have been done to find any type of link between cancer and radiation from x-rays