General Science MCQ Practice

• Reason: Electromagnetic waves can propagate in vacuum because they are oscillating electric and magnetic fields that sustain each other per Maxwell’s equations.
• Key concept: No medium is required; speed in vacuum is c ≈ 3×10^8 m/s.
• Why others are incorrect: Mechanical waves need a medium (air, water, solids) to travel; reverse and inverted waves are not classifications for media propagation.
• Exam tip: If a wave can travel in vacuum, it is electromagnetic.

• Answer: C. Infrasonic
• Sound waves with frequency < 20 Hz are called infrasonic.
• Key concept: Audible range for humans is about 20 Hz to 20 kHz; frequencies below are infrasonic and usually not heard but can affect animals and machines.
• There is no special formula; simply compare frequency to 20 Hz threshold.

• Reason: Producer gas is a mixture of combustible gases (CO and H2) with nonflammable gases (N2 and CO2) produced by gasifying coal/coss. It is used in old gas engines and metallurgy.
• Key concept: Gasification/reducing gas; CO + H2 are flammable; N2 and CO2 are inert-ish at low temps.
• Why others are wrong: Laser Star Gas is not a known standard term; Laughing Gas is N2O; Breathing Gas refers to air/oxygen supplies for respiration.
• Exam tip: remember “producer gas = CO + H2 + N2 + CO2” to distinguish from breathable or other industrial gases.

• Why: Shadows form when an object blocks light from a source. Opaque objects do not let light pass through, creating a dark region behind them.
• Key concept: Light travels in straight lines; shadows occur due to obstruction by an opaque object.
• Formula/numerical logic: Light ray from source to screen is blocked by object, creating a shadow on the side opposite the light.
• Why others are incorrect: - Transparent objects let light pass through, no shadow on the opposite side. - Luminous objects emit light; they produce light, not shadows by blocking light. - Translucent objects scatter light, causing partial blur, not a clear shadow.

Exam tip: If the object is seen clearly silhouetted, it is likely opaque.

• Nephron is the structural and functional unit of the kidney. It carries out filtration, reabsorption, and secretion to form urine.
• Key concept: Structure–function unit. Each kidney has millions of nephrons with a renal corpuscle and tubule system.
• Formula/logic (brief): Filtration at the glomerulus > Reabsorption and secretion along the tubule = urine formation.
• Exam tip: Remember “nephron = kidney’s worker.”
• Why others are incorrect: Pits, Nutrofil, and Tentacle are not kidney structures or units.

• Entomology is the study of insects.
• Key concept: biological classification and the study of insect life, anatomy, ecology, and behavior.
• Why others are incorrect: A—origin/history of terms (etymology); C—formation of rocks (geology); D—behaviour of humans (psychology/anthropology).
• Exam tip: If a term ends with "-ology", think about the subject field it studies.

• Chadwick experimentally showed the existence of neutrons in 1932, completing the basic nuclear model by proving a neutral particle inside the nucleus.
• Key concept: Neutron is a neutral, virtually mass-equal to a proton; essential for nuclear stability.
• Tip: Recall “n” stands for neutron; Chadwick = neutron discovery.
• Why others are incorrect: Thomson discovered the electron; Rutherford proposed the nucleus; Bohr introduced the model of quantized orbits.