General Science MCQ Practice

• Why it’s correct: Prolonged exposure to noise above about 80 dB can damage hearing and cause hazardous noise pollution. The higher the dB, the more intense the sound.
• Key concept: Decibels (dB) measure sound intensity. Health guidelines warn of risks when exposure exceeds certain thresholds; duration also matters (inverse relation).
• Small formula/idea: Risk increases with exposure time; roughly, longer exposure at high dB raises cumulative damage even if peak is brief.
• Why others are incorrect: 50 dB is normal sound; 100 dB is hazardous with shorter exposure; 130 dB causes immediate pain, not the general hazardous exposure threshold.
• Exam tip: Remember common threshold around 80–85 dB for hazardous noise; focus on exposure duration too.

• The correct answer is A. Origin of Universe.
• Big Bang theory describes how the universe began from a hot, dense state and has been expanding ever since.
• Key concept: cosmic expansion (Hubble's law v = H0 × d) and evidence like the cosmic microwave background radiation.
• Other options are incorrect: it does not explain the origin of the Sun (B) or laws of chemistry (C) or history (D).

• Concept: Tides are strongest when the Sun and Moon align with the Earth, their gravitational forces add up (spring tides).
• Reason: At the full moon (and also at the new moon), Sun–Earth–Moon are in a straight line, boosting tidal forces, causing the highest tides.
• Why others are wrong: Solar eclipse, lunar eclipse, and volcanoes do not determine tide height.
• Note: The formula varies as F ∝ GMm/r^2; combined Sun–Moon gravity increases tide range.

Exam tip: Remember "full moon = strong tides" as part of spring tides.

• Coal is a fossil fuel formed from ancient plant matter under high pressure and heat for millions of years, storing chemical energy as hydrocarbons.
• Key concept: Fossil fuels are non-renewable energy sources derived from ancient bio-matter.
• Exam tip: Remember fossil fuels include coal, oil, and natural gas (not renewable sources).
• Why others are incorrect:
  • Solar energy – renewable
  • Quartz – mineral, not an energy source
  • Lava – molten rock, not an energy resource

• The key concept is ozone’s ability to absorb ultraviolet (UV) radiation in the stratosphere, protecting life on Earth.
• Ozone (O3) absorbs most of the Sun’s harmful UV-C and UV-B rays, reducing DNA damage and skin/eye harm.
• Formula: O2 + UV -> 2O (atomic) + O3 formation in the stratosphere helps shield us.

• Reason: A vector has both magnitude and direction. Velocity gives how fast and in what direction an object moves, unlike scalars.
• Key concept: Vector vs scalar; velocity = displacement/time (m/s) with direction.
• Why others are incorrect:
  • Mass: scalar (only magnitude).
  • Volume: scalar (only magnitude).
  • Speed: scalar (magnitude only, no direction).

• Key concept: Hemoglobin in red blood cells binds O2 in lungs and releases it to tissues; this is how oxygen is transported.
• Why others are wrong: White blood cells, hormones, and enzymes do not carry oxygen to cells.
• Brief formula/logical note: O2 loading in lungs depends on high PO2; O2 unloading in tissues depends on low PO2 and Hb affinity changes (allosteric effects).
• Exam tip: Remember RBCs plus Hb is the main oxygen transporter, not plasma components.

• Biogas is produced from anaerobic digestion of organic waste, a renewable and non-conventional energy source.
• Concept: renewable biofuel from biomass; simple chemical idea is gas (mainly methane) produced from waste.
• Other options are fossil fuels or traditional biomass: Firewood is traditional biomass; Diesel and Petrol are fossil fuels.