Explanation

• Stars produce energy by combining lighter nuclei into heavier nuclei in their cores.
• In the core of a star, hydrogen nuclei fuse to form helium.
• This process releases a huge amount of energy in the form of light and heat.
• It is the primary source of a star’s energy and sustains its radiation for billions of years.

Last verified on 17-03-2026

Explanation

• Leaves have thin veins called vascular bundles.
• Veins consist of xylem and phloem for transport.
• Xylem transports water and minerals from roots to leaves.
• Phloem transports food (sugars) from leaves to other parts of the plant.

Last verified on 17-03-2026

Explanation

• Phosphorus (P), Potassium (K), and Nitrogen (N) are three essential macronutrients for plant growth.
• It is also referred to as "NPK".
• They play critical roles in various plant processes, including photosynthesis, root development, and cell growth.

Last verified on 17-03-2026

Explanation

• A permanent magnet retains its magnetism for a long time.
• It is hard to magnetize but difficult to demagnetize once magnetized.
• Made from hard magnetic materials like steel or alnico.
• Unlike temporary magnets, it does not lose its magnetism easily.

Last verified on 17-03-2026

Explanation

• The velocity of a wave depends on its wavelength and frequency.
• Formula: v = λ × f, where λ is wavelength and f is frequency.
• This applies to sound waves, light waves, and water waves.
• Higher frequency or longer wavelength increases the wave’s velocity if the medium is constant.

Last verified on 17-03-2026

Explanation

• An echo is a sound that reflects off a surface and is heard again.
• It occurs when sound waves bounce back from a distant surface like a wall or mountain.
• Echoes are common in caves, valleys, and empty halls.
• The reflected sound is perceived after a short delay.

Last verified on 17-03-2026

Explanation

• Total internal reflection occurs when light travels from a denser medium to a rarer medium.
• The angle of incidence must be greater than the critical angle for the two media.
• Light is completely reflected back into the denser medium instead of refracting.
• Common examples: optical fibers, diamonds, and mirages.

Last verified on 17-03-2026

Explanation

• Ions are charged particles formed when an atom gains or loses electrons.
• Loss of electrons creates a positively charged ion (cation).
• Gain of electrons creates a negatively charged ion (anion).

Last verified on 17-03-2026

Explanation

• A change in physical appearance or state of a substance, such as a change in shape, size, color, or phase (solid, liquid, gas), is called a Physical Change.
  

The are examples of Physical Changes:

• Melting (ice cream, wax, chocolate, ice and change from solid to liquid)
• Phase changes (boiling, freezing, condensation)
• Crushing (chalk)
• Tearing (paper)
• Crumpling (aluminium foil)
• Stretching (rubber band)
• Mixing (sugar in water)
• Dissolving (sugar, salt in water)
• Moulding (clay, metals)
• Slicing (fruit)
• Forming of frost (from water vapors)
• Transition to a gas (change from liquid to gas)
• Change of durability (change in texture or strength)
• Changes to crystal form (change in crystal structure)

Last verified on 17-03-2026

Explanation

• A mature, large ovary and seed are characteristics of a fruit.
• A fruit is the mature ovary of a plant, which contains seeds.
• It typically surrounded by a fleshy, edible pulp.

Last verified on 17-03-2026