Q6(c). Write briefly on the following: LASER (Light Amplification by Stimulated Emission of Radiation); CFCs (Chlorofluorocarbons); Radioisotopes; DNA (Deoxyribonucleic Acid)

LASER (Light Amplification by Stimulated Emission of Radiation)

A laser is a device that emits highly coherent, monochromatic and directional light through stimulated emission.

Principle

• Stimulated emission (Einstein, 1917).
• Atoms excited to higher energy levels emit photons of identical phase and wavelength and coherent light.

Properties

• Highly directional,
• Monochromatic,
• High intensity,
• Coherence.

Applications

• Medicine: Eye surgeries (LASIK), dermatology.
• Industry: Cutting, welding, barcode scanning.
• Defence: Range finders, laser-guided missiles.
• Communication: Optical fibre networks.
• Research: Holography, spectroscopy.

CFCs (Chlorofluorocarbons)

CFCs are organic compounds containing chlorine, fluorine, and carbon. Chemically stable, non-toxic, and non-flammable.

Sources/Uses

• Refrigerants (Freon),
• Aerosol sprays,
• Foam blowing agents,
• Fire extinguishers.

Environmental Impact

• Major ozone-depleting substances (ODS).
• Global warming potential thousands of times higher than CO₂.
• Cause ozone hole formation (Antarctica).

International Action

Montreal Protocol (1987) mandated phasing out CFCs globally.

Radioisotopes

Radioisotopes are unstable isotopes of elements that emit radiation (alpha, beta, gamma) to attain stability.

Applications

• Medicine:
  • Cancer therapy (Co-60, I-131),
  • Diagnostic imaging (PET scans using F-18).
• Agriculture:
  • Mutation breeding,
  • Food irradiation,
  • Pest control.
• Industry:
  • Radiography for weld testing,
  • Gauging thickness of materials.
• Research:
  • Tracing chemical pathways,
  • Carbon dating (C-14).

Radioisotopes are regulated due to radiation hazards.

DNA (Deoxyribonucleic Acid)

DNA is the genetic material present in all living organisms (except some viruses). It carries hereditary information and controls protein synthesis.

Structure

Double-helix model (Watson & Crick, 1953),

• Composed of nucleotides:
  • Sugar (deoxyribose),
  • Phosphate group,
  • Nitrogenous bases (A, T, G, C).

Base pairing: A–T and G–C.

Functions

• Stores genetic information,
• Controls cell division and growth,
• Enables inheritance,
• Guides protein synthesis via mRNA.

Applications

• Genetic engineering,
• DNA fingerprinting (forensics),
• Genome editing (CRISPR),
• Gene therapy,
• Biotechnology and crop improvement.