The Yellow Revolution in India refers to the significant increase in the production of oilseeds. It was initiated to make India self-sufficient in edible oils such as mustard, sunflower, groundnut, and soybean oils. The revolution gained momentum under the Technology Mission on Oilseeds (TMO) launched in the 1980s. The key figure associated with the Yellow Revolution is Sam Pitroda.

Other options (for context)

• Cereals: Their production growth is linked with the Green Revolution.
• Milk: Related to the White Revolution led by Dr. Verghese Kurien.
• None of these: Incorrect — the Yellow Revolution specifically concerns oilseeds.

Explanation: The terms Dolby B and Dolby C refer to noise reduction circuits used in tape recorders and sound systems. These technologies reduce background hiss and unwanted noise during playback and recording, thereby improving the overall sound quality.

Adolf Gaston Eugen Fick, a German physiologist, invented the first successful contact lens in 1888. His design consisted of a glass lens that covered the entire eye, resting on the sclera (the white part of the eye). Though bulky and uncomfortable by today’s standards, it laid the foundation for modern soft and gas-permeable contact lenses used in vision correction and cosmetics.

Other options (for context)

• Enrico Fermi: Known for his work in nuclear physics and development of the first nuclear reactor.
• Sandford Fleming: Introduced the concept of standard time zones.
• Benoit Fourneyron: Invented the water turbine, not related to optics or vision correction.

One molecule of a Chlorofluorocarbon (CFC) can destroy up to 1,00,000 molecules of ozone (O₃) in the ozone layer. When CFCs reach the stratosphere, they are broken down by ultraviolet (UV) radiation, releasing chlorine atoms. Each chlorine atom acts as a catalyst in the breakdown of ozone molecules, significantly depleting the protective ozone layer that shields Earth from harmful UV rays.

Other options (for context)

• 10,000: Underestimates the destructive potential of a single CFC molecule.
• 10,00,000: Overestimates the number of ozone molecules destroyed.
• No one of the above: Incorrect — the correct answer is 1,00,000 molecules of ozone.

Explanation: The colour of the sky without an atmosphere would appear black. On Earth, the sky looks blue because molecules in the atmosphere scatter sunlight — a phenomenon called Rayleigh scattering. Shorter wavelengths of light (blue and violet) are scattered more than longer wavelengths (red). However, if there were no atmosphere to scatter sunlight, no light would be diffused in all directions, and the sky would appear completely dark or black, just as it does from the surface of the Moon or in outer space.

Silviculture is the branch of forestry concerned with the management, cultivation, and care of forests. It involves the practice of controlling the establishment, growth, composition, and quality of forest stands to meet diverse needs such as timber production, wildlife habitat, and environmental conservation. The term comes from Latin — silva meaning forest, and cultura meaning cultivation.

Other options (for context)

• Rivers: Managed under hydrology or water resource management, not silviculture.
• Lakes: Managed under limnology or aquatic resource management.
• Hills: May be part of forest areas, but silviculture specifically refers to forest management.

Explanation: The gas used for artificial ripening of green fruits is ethylene (C₂H₄). Ethylene is a natural plant hormone that regulates fruit ripening by stimulating the conversion of starches into sugars, making the fruit softer and sweeter. In artificial ripening, ethylene gas is introduced in controlled amounts to uniformly ripen fruits such as bananas, mangoes, and tomatoes. However, the use of harmful chemicals like calcium carbide for ripening is banned because it produces toxic substances like acetylene.

Explanation: The spectrophotometer measures bacterial growth by determining the optical density (OD) or turbidity of a culture. As bacteria multiply, the suspension becomes more turbid and absorbs more light. The absorbance value is proportional to the number of bacterial cells present.

In organic farming, chemical fertilizers are not used. Instead, farmers rely on natural manures, compost, and biofertilizers to enrich the soil. Organic farming avoids synthetic pesticides and focuses on maintaining ecological balance, soil fertility, and sustainable crop production.

• Intercropping: Often used to increase productivity naturally.
• Manures: Essential in organic farming for soil health.
• Biofertilizers: Widely used to promote natural nutrient availability.