This section covers common scientific principles, phenomena, and observations you encounter daily. Understanding these is crucial for competitive exams as they test your general awareness and application of basic science.
Physics in Everyday Life
- Light and Optics:
- Refraction: Bending of light as it passes from one medium to another (e.g., spoon appearing bent in water, shimmering of objects over a hot road, distant objects appearing hazy).
- Lenses:
- Concave Lens: Diverges light, used in spectacles for myopia (short-sightedness).
- Convex Lens: Converges light, used in spectacles for hypermetropia (long-sightedness), magnifying glasses, cameras, telescopes.
- Reflection: Bouncing back of light when it strikes a surface (e.g., mirrors).
- Plane Mirror: Forms virtual, erect, and same-sized image. Used in dressing mirrors.
- Concave Mirror: Converges light, forms magnified/diminished, real/virtual images. Used in shaving mirrors, dentists’ mirrors, car headlights (as reflectors).
- Convex Mirror: Diverges light, forms virtual, erect, diminished images. Used as rearview mirrors in vehicles (wider field of view).
- Total Internal Reflection (TIR): When light traveling from a denser to a rarer medium strikes the boundary at an angle greater than the critical angle, it reflects entirely back into the denser medium.
- Examples: Formation of mirage, sparkling of diamond, working of optical fibers (endoscopes, telecommunication).
- Dispersion of Light: Splitting of white light into its constituent colors (VIBGYOR) when passing through a prism due to different refractive indices for different wavelengths.
- Example: Formation of rainbow (water droplets act as tiny prisms).
- Scattering of Light: Dispersion of light by particles in the medium.
- Rayleigh Scattering: Explains why the sky is blue (blue light scatters more than red due to its shorter wavelength).
- Why clouds are white: Water droplets in clouds are large enough to scatter all wavelengths of light equally.
- Why sun appears red at sunrise/sunset: Blue light is scattered away more extensively when sunlight travels a longer path through the atmosphere, leaving primarily red light to reach our eyes.
- Sound:
- Nature: Longitudinal wave, requires a medium to travel (cannot travel in vacuum).
- Speed: Travels fastest in solids, then liquids, slowest in gases. (Steel > Water > Air).
- Pitch: Determined by frequency (higher frequency = higher pitch).
- Examples: Whistle (high pitch), lion’s roar (low pitch).
- Loudness: Determined by amplitude of the wave. Measured in decibels (dB).
- Echo: Reflection of sound from a surface. Requires a minimum distance (approx. 17.2 meters at 22°C) for the listener to distinguish between original and reflected sound.
- Reverberation: Multiple reflections of sound in an enclosed space, leading to persistence of sound.
- Heat & Temperature:
- Heat: Form of energy.
- Temperature: Measure of the degree of hotness or coldness of a body.
- Modes of Heat Transfer:
- Conduction: Transfer through direct contact (e.g., heating a metal rod). Predominant in solids.
- Convection: Transfer through movement of fluid (liquid or gas) particles (e.g., boiling water, sea breezes, land breezes). Predominant in liquids and gases.
- Radiation: Transfer through electromagnetic waves, does not require a medium (e.g., heat from the sun, heat from a fire).
- Good Conductors: Metals (copper, aluminum).
- Bad Conductors/Insulators: Wood, plastic, air, wool.
- Thermos Flask (Dewar Flask): Minimizes heat transfer by all three modes:
- Vacuum between walls: Prevents conduction and convection.
- Silvered surfaces: Reduce heat loss/gain by radiation.
- Stopper (cork/plastic): Prevents convection through the opening.
- Expansion/Contraction: Most substances expand on heating and contract on cooling.
- Anomalous expansion of water: Water contracts from 0°C to 4°C, then expands above 4°C. Water is densest at 4°C. This property is vital for aquatic life in cold regions.
- Pressure: Force per unit area.
- Atmospheric Pressure: Pressure exerted by the weight of the air above a surface. Measured by barometer. Decreases with altitude.
- Applications: Suction cups, drinking straw, syringe, siphon.
- Hydraulic Systems: Work on Pascal’s Principle (pressure applied to an enclosed fluid is transmitted undiminished to every portion of the fluid and the walls of the containing vessel).
- Examples: Hydraulic brakes, hydraulic lifts, jacks.
- Electricity & Magnetism:
- Conductors: Materials that allow electricity to pass through easily (metals, graphite, electrolytes).
- Insulators: Materials that resist the flow of electricity (plastic, rubber, wood, glass).
- Series Combination: Total resistance increases, current remains same, voltage divides.
- Parallel Combination: Total resistance decreases, voltage remains same, current divides. Household wiring is generally in parallel.
- Fuse: Safety device in an electrical circuit, melts and breaks the circuit if current exceeds a safe limit. Made of an alloy (tin-lead) with low melting point.
- Earthing: Provides a path for fault current to flow to the ground, preventing electric shocks.
- Electromagnetism: Moving electric charges produce magnetic fields.
- Examples: Electric bells, motors, generators, transformers.
- Magnets: Have North and South poles. Like poles repel, unlike poles attract.
- Uses: Compasses, refrigerators, speakers, MRI machines.
- Simple Machines: Devices that multiply force or change the direction of force.
- Lever: Fixed pivot (fulcrum). Three classes depending on position of fulcrum, load, and effort.
- Class 1 (Fulcrum in middle): See-saw, crowbar, scissors.
- Class 2 (Load in middle): Wheelbarrow, nutcracker, bottle opener.
- Class 3 (Effort in middle): Fishing rod, tongs, human forearm.
- Pulley: A wheel with a grooved rim over which a rope or cable passes. Can change direction of force or provide mechanical advantage.
- Inclined Plane: Ramp, makes it easier to move objects to a higher elevation.
- Wedge: Two inclined planes back-to-back (axe, knife).
- Screw: An inclined plane wrapped around a cylinder (screw, drill).
- Wheel and Axle: Door knob, steering wheel.
Chemistry in Everyday Life
- Acids, Bases, and Salts:
- Acids: Sour taste, turn blue litmus red. pH < 7. Release H+ ions in solution.
- Examples: Vinegar (acetic acid), lemon (citric acid), stomach acid (hydrochloric acid).
- Bases: Bitter taste, slippery, turn red litmus blue. pH > 7. Release OH- ions in solution.
- Examples: Baking soda (sodium bicarbonate), soap, antacids (magnesium hydroxide).
- Neutralization: Reaction between an acid and a base to form salt and water.
- Example: Antacids neutralizing stomach acid.
- pH Scale: Measures acidity/alkalinity (0-14). 7 is neutral.
- Importance: Soil pH for agriculture, blood pH, human skin pH.
- Common Chemical Compounds:
- Salt (NaCl): Common table salt, used as preservative.
- Baking Soda (Sodium Bicarbonate, NaHCO3): Used in baking as leavening agent, antacid.
- Washing Soda (Sodium Carbonate, Na2CO3): Used as cleaning agent, in glass manufacturing.
- Bleaching Powder (Calcium Oxychloride, CaOCl2): Used for bleaching cotton/linen, disinfectant.
- Limestone (Calcium Carbonate, CaCO3): Main component of marble, chalk, shells.
- Quicklime (Calcium Oxide, CaO): Used in cement, steel manufacturing.
- Slaked Lime (Calcium Hydroxide, Ca(OH)2): Used in whitewashing.
- Plaster of Paris (Calcium Sulfate Hemihydrate, CaSO4.1/2H2O): Used for fractures, statues, decorative material.
- Gypsum (Calcium Sulfate Dihydrate, CaSO4.2H2O): Used to make Plaster of Paris, as a fertilizer.
- Changes Around Us:
- Physical Change: No new substance formed, easily reversible.
- Examples: Melting of ice, boiling water, dissolving sugar in water, tearing paper.
- Chemical Change: New substance(s) formed, generally irreversible.
- Examples: Burning of wood, rusting of iron, cooking food, ripening of fruit, digestion, curdling of milk.
- Combustion & Fuels:
- Combustion: Chemical process that releases energy as heat and light, usually involves reaction with oxygen.
- Ignition Temperature: Minimum temperature at which a substance catches fire.
- Fire Extinguishers: Use various methods to extinguish fire:
- Water: Cools the fuel below its ignition temperature, cuts off oxygen supply (for Class A fires: wood, paper). Not for electrical/oil fires.
- CO2: Denser than air, smothers fire by cutting off oxygen supply (for electrical, oil fires).
- Sand: Smothers fire.
- Fuels: Substances that produce heat upon burning.
- Solid: Coal, wood, charcoal.
- Liquid: Petrol, diesel, kerosene, LPG (Liquefied Petroleum Gas – propane, butane).
- Gaseous: CNG (Compressed Natural Gas – methane), Biogas (methane, CO2).
- Corrosion: Deterioration of a material, usually metal, due to reaction with its environment.
- Rusting: Corrosion of iron and steel, requires both oxygen and water. Forms reddish-brown flaky substance (iron oxide).
- Prevention: Painting, oiling, greasing, galvanizing (coating with zinc), electroplating, alloying.
- Polymers & Plastics:
- Polymers: Long chains of repeating small units (monomers).
- Plastics: Synthetic polymers.
- Thermoplastics: Can be softened by heating and molded repeatedly (e.g., PVC for pipes, PET for bottles, polythene for bags). Recyclable.
- Thermosetting Plastics: Once molded and set, cannot be softened by heating (e.g., Bakelite for electrical switches, Melamine for dinnerware). Non-recyclable.
- Biodegradable vs. Non-biodegradable: Plastics are generally non-biodegradable, accumulating in the environment.
Biology in Everyday Life
- Human Body Systems:
- Digestive System: Breaks down food into absorbable nutrients. Begins in mouth (saliva contains amylase), stomach (HCl, pepsin), small intestine (most absorption), large intestine (water absorption).
- Respiratory System: Exchange of gases (oxygen in, carbon dioxide out). Lungs are primary organs. Diaphragm plays a key role in breathing.
- Circulatory System: Transports blood (oxygen, nutrients, hormones) throughout the body. Heart pumps blood. Arteries carry oxygenated blood away from heart, veins carry deoxygenated blood to heart.
- Nervous System: Controls and coordinates body functions. Brain, spinal cord, nerves. Neuron is the basic unit.
- Skeletal System: Provides support, structure, protection, and allows movement (206 bones in adults).
- Muscular System: Enables movement.
- Excretory System: Removes waste products. Kidneys filter blood.
- Nutrition:
- Carbohydrates: Primary energy source (sugars, starch).
- Fats: Concentrated energy source, insulation, protection of organs.
- Proteins: Building blocks of body tissues, enzymes, hormones.
- Vitamins: Essential organic compounds required in small amounts for various metabolic functions.
- Fat-soluble (ADEK): Stored in body.
- Water-soluble (BC): Not stored, need regular intake.
- Minerals: Inorganic elements essential for body functions (calcium for bones, iron for blood).
- Water: Crucial for all bodily functions (solvent, transport, temperature regulation).
- Diseases and Health:
- Communicable/Infectious Diseases: Spread from person to person or from animals/environment to person.
- Caused by: Bacteria (TB, cholera), Viruses (Flu, common cold, AIDS, COVID-19), Fungi (ringworm), Protozoa (malaria, amoebiasis).
- Prevention: Vaccination, hygiene (hand washing), sanitation, safe food/water.
- Non-communicable/Lifestyle Diseases: Not spread from person to person.
- Examples: Diabetes, heart disease, cancer, hypertension.
- Prevention: Healthy diet, exercise, avoiding smoking/excess alcohol.
- Vaccines: Prepare the immune system to fight off specific diseases by introducing a weakened or inactivated form of the germ.
- Antibiotics: Medications that kill or inhibit the growth of bacteria. Ineffective against viruses.
- Plants and Agriculture:
- Photosynthesis: Process by which green plants convert light energy into chemical energy (glucose) using CO2 and water. Releases oxygen. Chlorophyll is essential.
- Pollination: Transfer of pollen from anther to stigma. Can be self-pollination or cross-pollination (by wind, water, insects, animals).
- Fertilizers: Substances added to soil to provide nutrients for plant growth (NPK – Nitrogen, Phosphorus, Potassium).
- Pesticides: Chemicals used to kill pests (insects: insecticides, weeds: herbicides, fungi: fungicides).
- Crop Rotation: Growing different crops in succession on the same land to improve soil fertility and control pests.
- Types of Crops (India):
- Rabi Crops: Sown in winter (Oct-Dec), harvested in spring (Apr-Jun). E.g., Wheat, barley, gram, mustard.
- Kharif Crops: Sown in rainy season (Jun-Jul), harvested in autumn (Sep-Oct). E.g., Rice, maize, jowar, bajra, cotton.
- Zaid Crops: Short duration crops grown between Rabi and Kharif. E.g., Watermelon, muskmelon, cucumber.
- Ecology & Environment:
- Biodiversity: Variety of life on Earth.
- Ecosystem: Community of living organisms interacting with their non-living environment.
- Food Chain/Web: Shows feeding relationships.
- Pollution: Introduction of harmful substances or products into the environment.
- Air Pollution: Particulate matter, CO, SO2, NOx.
- Water Pollution: Industrial waste, sewage, agricultural runoff.
- Soil Pollution: Pesticides, industrial waste, plastic.
- Greenhouse Effect: Natural process where certain gases (CO2, methane, water vapor) trap heat in Earth’s atmosphere, warming the planet. Enhanced by human activities leading to global warming.
- Ozone Layer Depletion: Thinning of the ozone layer (O3) in the stratosphere, mainly due to CFCs. Protects Earth from harmful UV radiation.
- Conservation: Protecting natural resources and ecosystems.
General Awareness & Current Science Trends
- Technology in Daily Life:
- Internet of Things (IoT): Network of physical objects embedded with sensors and software for connection and exchange of data over the internet (smart homes, wearables).
- Artificial Intelligence (AI): Machine intelligence designed to mimic human cognitive functions (voice assistants, recommendation systems, self-driving cars).
- 5G Technology: Fifth generation of cellular technology, promises much higher speeds, lower latency, and greater capacity.
- Renewable Energy Sources: Solar, wind, hydro, geothermal, biomass. Importance for sustainable development and reducing carbon footprint.
- Scientific Discoveries & Concepts:
- Big Bang Theory: Predominant cosmological model explaining early development of the universe.
- Black Holes: Regions of spacetime where gravity is so strong that nothing, not even light, can escape.
- Genetic Engineering/CRISPR: Technologies that allow modification of an organism’s DNA, with applications in medicine, agriculture.
- Stem Cells: Undifferentiated cells with potential to develop into many different cell types. Research area with therapeutic potential.
- Common Mnemonics (Science):
- VIBGYOR: Colors of the rainbow (Violet, Indigo, Blue, Green, Yellow, Orange, Red).
- “My Very Educated Mother Just Served Us Noodles”: Planets in order from Sun (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune).
WATER is a common DENSER liquid, but ICE is LESS DENSE*: Helps remember anomalous expansion of water, why ice floats.
- “RABID DOGS”: Diseases spread by rats, animals, birds, insects, pests (often vector-borne).
- King Philip Came Over For Good Soup: Kingdom, Phylum, Class, Order, Family, Genus, Species (Taxonomic classification).
Key Highlights for Revision
- Focus on ‘Why’ and ‘How’: Don’t just memorize facts; understand the underlying principles.
Example:* Why is the sky blue? How does a fuse work?
- Application-Oriented Questions: Many questions will relate concepts to everyday scenarios.
Example:* Why do we wear light-colored clothes in summer? (Reflection of heat)
- Interlink Concepts: Science is interconnected.
Example:* Understanding pH for soil fertility (biology) and for antacids (chemistry).
- Basic Units & Measurements: Know common units (e.g., force-Newton, energy-Joule, power-Watt, current-Ampere, resistance-Ohm).
- Disease Prevention and Health: Basic hygiene, common vaccines, lifestyle effects.
- Environmental Concerns: Pollution types, global warming, renewable energy.
- Technology Impact: How new technologies affect daily life.
By focusing on these practical aspects and understanding the scientific reasoning behind everyday phenomena, you will be well-prepared for the General Knowledge section of competitive exams.
