Explanation

• The first compound microscope is believed to have been invented around 1590.
• It was developed by the Dutch spectacle makers Hans Janssen and his son Zacharias Janssen.
• Their invention used two lenses to magnify tiny objects.

Additional information:

• Galileo Galilei – 1609 improved the microscope design
• Robert Hooke – 1665 observed cork cells and wrote Micrographia
• Antonie van Leeuwenhoek – 1674 discovered microorganisms
• Joseph Jackson Lister – 1830 improved modern compound microscope

Last verified on 13-03-2026

Explanation

• Thermodynamics studies the relationship between heat, temperature, energy, and work.

Additional information:

• First law: Energy cannot be created or destroyed (Law of energy conservation)
• Second law: Heat flows from hot to cold spontaneously
• Third law: Absolute zero cannot be reached
• Zeroth law: Establishes temperature measurement
• Applications: Engines, refrigerators, heat pumps, and power plants

Last verified on 13-03-2026

Explanation

• The symbol ⁴₂He indicates helium has 2 protons (atomic number = 2) and mass number = 4.
• In a neutral atom, the number of electrons = protons, so helium has 2 electrons.

Last verified on 13-03-2026

Explanation

Definition: Possess both magnitude and direction.

Representation: Represented by arrows, where the length indicates magnitude and the arrowhead indicates direction.

Examples: 

• Displacement
• Velocity
• Acceleration
• Force
• Momentum

Additional information 

Difference from Scalars: Unlike scalars, which only have magnitude (e.g., speed), vectors require both to be fully defined

Last updated on 09-03-2026

Explanation

• Weight is a vector quantity
• Because it is a force defined as the product of mass and the acceleration due to gravity (W = mg).
• It has both magnitude (amount of force) and direction (downward, towards the center of the Earth)

Additional information 

Mass,  Time, and temperature are scalar quantities

Last updated on 09-03-2026

Explanation

Scalar quantities are physical quantities that have only magnitude (amount or size) but no direction.

Examples of scalar quantities include:

• Mass
• Temperature
• Time
• Energy
• Distance

Last verified on 07-02-2026

Explanation

• Taxonomy is the science of classifying and naming organisms.
  • Helps organize plants, animals, and microorganisms into groups.
  • Based on shared characteristics, genetics, and evolutionary relationships.
  • Developed initially by Carl Linnaeus in the 18th century.

Last verified on 06-02-2026

Explanation

• Some organisms feed on dead and decaying organic matter instead of living organisms.
• These organisms are called saprotrophs.
• They play an important role in decomposition and nutrient recycling in ecosystems.
• Examples include fungi, bacteria, and some protists.

Last verified on 01-02-2026

Explanation

• Transpiration is the process by which plants lose water in the form of vapor from leaves, stems, and flowers.
• It helps in cooling the plant, nutrient transport, and maintaining water balance.

Additional information:

• Evaporation: Water loss from soil or water surfaces
• Respiration: Energy release by breaking down sugars
• Photosynthesis: Production of food using sunlight, CO₂, and water

Last verified on 27-01-2026

Explanation

The mass of Earth is approximately 6.0 x 10^24 kilograms (5.98 x 10^24 kg).

This is a widely accepted scientific value, based on various measurements and calculations, including:

• Gravity measurements
• Satellite orbits
• Seismological data
• Planetary formation models