Explanation

• The centrosome is a small non-membranous organelle found mainly in animal cells.
• It plays a key role in cell division (mitosis and meiosis) by organizing the spindle fibers.
• It contains two centrioles arranged at right angles.
• The centrosome ensures proper separation of chromosomes during cell division.

Last verified on 13-03-2026

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