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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)