Explanation

• Hydropower is electricity generated from flowing or falling water.
• It uses dams and rivers to produce energy.
• It is a clean and renewable energy source.
• Famous example: Dams like Tarbela and Mangla in Pakistan produce hydropower electricity.

Last verified on 07-05-2026

Explanation

• Cell membrane is the outer protective covering of the cell.
• It controls what enters and leaves the cell.
• It works like a selective barrier.
• Also called plasma membrane.
• Allows useful substances in and waste out.
• Maintains balance inside the cell (homeostasis).

Last verified on 07-05-2026

Explanation

• Vitamin D is essential for strong bones and teeth.
• It helps the body absorb calcium and phosphorus.
• Its deficiency causes Rickets in children.
• Vitamin D = “Sunshine vitamin”
• Helps in bone mineralization
• Works with calcium to build strong skeleton

Last verified on 07-05-2026

Explanation

• Laser light is monochromatic, meaning it has one color.
• It contains only one wavelength and one frequency.
• This makes laser light very pure and focused.
• They are used in surgery, barcode scanners, and fiber optics communication.

Additional information:

• Polychromatic (white light) → Multiple wavelengths

Last verified on 07-05-2026

Explanation

• Isobars are atoms of different elements.
• They have same mass number but different atomic number.
• They show different chemical properties but same nuclear mass.
• Example: Argon-40 and Calcium-40 both have mass number 40 but different atomic numbers.

Last verified on 07-05-2026

Explanation

• Alpha, Beta, Gamma, and X-rays are types of radiation.
• In an electric field, charged particles are deflected.
• Beta radiation is light and carries a negative charge, so it bends the most.

Additional information:

Deflection in Electric Field (Comparison)

• Alpha (α) rays → Less deflected (heavy mass + positive charge)
• Gamma (γ) rays → No deflection (no charge)
• X-rays → No deflection (neutral electromagnetic waves)

Last verified on 07-05-2026

Explanation

• The atomic number of an element is equal to the number of protons present in its nucleus.
• If the number of protons increases, the element itself changes because its atomic number changes.
• Protons are positively charged particles.
• The mass number is calculated by adding protons and neutrons.

Last verified on 07-05-2026

Explanation

• Wind energy depends on wind speed, which is not constant all the time.
• If the wind stops or becomes weak, electricity production also decreases.
• This making it less reliable for uninterrupted large-scale power generation.
• It is a renewable and environmentally friendly source of energy.
• Countries like China, the USA, and Germany are among the largest producers of wind power.

Last verified on 07-05-2026

Explanation

• Quantum theory states that energy levels in atoms are discrete (fixed and separate).
• Electrons can only exist in specific energy levels, not in between.
• They absorb or emit energy when moving from one level to another.

Last verified on 06-05-2026

Explanation

• In the photoelectric effect, electrons are emitted only if light has a minimum required frequency (threshold frequency).
• Increasing intensity alone cannot eject electrons if frequency is too low.
• Thus, frequency of light is the key factor.

Last verified on 06-05-2026