Summary

Science and Technology Class 07

A brief discussion on the previous Class (5:09 PM)

Radioactivity(5:51 PM)

Certain nuclei are not very stable.
To attain stability they emit particles, which are called alpha, beta, and gamma.
(*refer to the video of the class for equation)
An alpha particle is helium nuclei.
In alpha decay, the atomic number decreases by 2 and the atomic mass by 4.
In beta decay, the beta particle can be an electron or positron.
A beta particle is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide.
This means the atomic number increases by 1, but the atomic mass doesn't change.
Gamma is a high-energy light particle.
Radioactive samples, decay following a relationship, where their number becomes half and half in the constant time.
This time is called the half-life.
For example, carbon-14 has a half-life of 5730 years.
Radioactive isotopes are found naturally, and can also be made in labs.
Such reactions have a lot of applications, for example

Applications of Radioactivity (5:59 PM)

Applications in agriculture
(a) Plant Mutation Breeding
Plants, buds, and seeds can be exposed to gamma radiation, leading to mutations, and perhaps a few of those mutations will be desirable. For example, resistance to drought, salinity, etc.
(b) Fertilizer efficiency
Radioisotope of nitrogen or phosphorous in the very small traces can be added to the normal fertilizer, and how much absorption by plants has occurred can be measured.
(c) Food Processing
Exposing food items to gamma rays, x-ray, electron beams, etc, can kill microbial organisms.
It will enhance the shelf life of food and can also control food-borne diseases.
Such methods are called food irradiation.
Application in Medicine
(a) External beam therapy
cancerous growth is exposed to gamma radiation so that the tumour can be destroyed. Cobalt-60 is used here.
(b) Brachytherapy
It is an advanced cancer treatment method, where a radioisotope is placed near the tumour so that only the tumour is destroyed, with minimal effect on the healthy cell. (Iridium 192 is used in Brachytherapy)
(c) Proton Beam Therapy
Rather than using Gamma, a proton beam is used. It is effective in destroying cancer with very less side effects.
(d) Nuclear Medicine
Nuclear medicines work as radiotracers. They are radioactive.
Once injected into the body, the interaction of Gamma with healthy and cancerous cells can be recorded.
(e) Radiation sterilization
With the help of Gamma-ray, syringes, gloves, dressings, medical equipment, etc. can be sterilized to kill microbial organisms.
Application in Space
(a) Radioisotope Thermoelectric Generator
For deep space missions, solar energy is not a reliable source of energy for such missions, a radioisotope, such as Plutonium-238 is used, which emits an alpha particle and energy.
This energy can be used as thermal energy which can also be converted into electrical energy.
NASA has used this many times. ISRO is exploring this technology.
(b) Nuclear Propulsion (6:47 PM)
It remains in the experimental stages.
The goal is to propel a rocket with nuclear fission.
Such propulsion will be helpful for future interplanetary manned missions.
Applications in Industry (7:18 PM)
(a) Use of gamma rays to find defects in solid materials.
(b) Use of radiotracers to find any type of leakage.
(c) Use of nuclear power for water desalination.
(d) Use of carbon dating in geology, archaeology, and anthropology.

Nanotechnology (7:40 PM)

1 nanometer(nm) = 10^-9 meter
Nanotechnology is science, technology, and engineering associated with nanomaterials with 1-100 nm dimensions.
Nanomaterials exhibit amazing properties compared to their macro counterparts.
They can exhibit higher strength, lighter weight, increased control of the light spectrum, and great chemical reactivity.
Uniqueness of Nanotechnology
(a) At the nanoscale, quantum effects decide the property of the material.
The property becomes a function of size, that is, by changing the size scientists can finetune the property.
For example, Quantum dots.
(b) Nanomaterials generally have high chemical reactivity because of increased surface area, compared to the same volume.
This also makes them better catalysts.
Increased surface area leads to more atomic and molecular interactions, which enhances chemical reactivity.

The topics for the Next Class: Nanotechnology (continued)