Explanation

• Starlight passes through Earth’s atmosphere.
• Different air layers have different densities and temperatures.
• Light is repeatedly refracted (bent).
• This causes the star’s brightness to appear to change rapidly.
• This apparent change is called twinkling (scintillation).

Last verified on 26-10-2026

Explanation

• The nucleus contains the cell’s genetic material (DNA).
• DNA carries hereditary information.
• The nucleus controls many cell activities.
• In prokaryotic cells (like bacteria), DNA is not enclosed in a nucleus; it is found in the nucleoid region.
• Genetic material = DNA.

Explanation

• Earth’s gravity provides the force that keeps satellites in orbit.
• This gravitational force pulls the satellite toward Earth.
• The satellite’s forward motion makes it continuously fall around Earth rather than directly into it.
• Newton’s Law of Gravitation explains this gravitational attraction.

Explanation

Bernoulli’s principle is based on conservation of energy in flowing fluids.

P+1/2 ρv2+ρgh=constant

For airplane wings:

• P = Pressure
• ρ (rho) = Density of air
• v = Speed of air
• g = Gravitational acceleration
• h = Height
• Higher air speed → Lower pressure
• Lower air speed → Higher pressure
• Pressure difference between the upper and lower surfaces creates lift.
• Lift acts upward and helps the airplane fly

Explanation

• Carbon dioxide (CO₂) is used in fire extinguishers.
• It extinguishes fire by displacing oxygen and cooling the burning material.
• CO₂ fire extinguishers are especially effective for electrical and flammable liquid fires.
• Carbon dioxide is a colorless and non-flammable gas.
• It leaves no residue after use.

Explanation

• Amylase breaks down starch.
• Starch → Maltose + smaller sugars.
• Found in saliva and pancreatic juice.
• Salivary amylase starts starch digestion in the mouth

Explanation

• O⁻ (O Negative) is the universal donor blood group.
• It can be transfused to A, B, AB, and O blood groups.
• O⁻ blood lacks A, B, and Rh (D) antigens.

Additional information:

• Universal Recipient: AB⁺ (AB Positive)
• ABO Blood Groups: A, B, AB, O
• Rh Types: Positive (+) and Negative (−)
• Total Common Blood Groups: 8 (A⁺, A⁻, B⁺, B⁻, AB⁺, AB⁻, O⁺, O⁻)

Last verified on 14-07-2026

Explanation

• Nicolaus Copernicus proposed the heliocentric model.
• Heliocentric means the Sun is at the center.
• Earth and other planets revolve around the Sun.
• Proposed in the 16th century.
• Ptolemy supported the geocentric model (Earth-centered).

Explanation

• Ice is less dense than water, so it floats.
• Archimedes’ Principle explains the buoyant force acting on floating ice.
• The buoyant force acts upward against gravity.
• Formula: FB = p Vg
• Key point: An object floats when buoyant force = its weight.

Explanation

• Win + R opens the Run dialog box in Windows.
• It allows users to quickly open programs, folders, files, and system tools by typing commands

Additional Information:

• cmd: Opens the Command Prompt.
• notepad: Opens Notepad.
• msconfig: Opens System Configuration.
• control: Opens the Control Panel

Last updated 07-09-2026 by NA