Explanation

• The SI unit of sound intensity is watt per square meter (W/m²).
• Sound intensity is the amount of sound power passing through a unit area.
• It shows how strong or weak a sound wave is at a particular point.
• Sound intensity decreases as the distance from the source increases.
• Decibel (dB) is used to measure sound intensity level, not the actual intensity

Last verified on 20-07-2026

Explanation

• Pakistan's standard household electricity supply is 220–240 V AC at 50 Hz.
• The frequency of alternating current (AC) is 50 cycles per second (50 Hz).
• This standard is used for homes, schools, offices, and most electrical appliances in Pakistan.

Last verified on 19-07-2026

Explanation

• In 1924, Louis de Broglie proposed that matter has both particle and wave properties.
• This concept is known as the De Broglie Hypothesis or Matter Wave Theory.
• It became one of the foundations of Quantum Mechanics.

Last verified on 19-07-2026

Explanation

• The Universe is continuously expanding.
• Age of the Universe: ≈13.8 billion years
• Big Bang: ≈13.8 billion years ago
• Hubble's discovery: 1929
• Cosmic Microwave Background discovered: 1965
• Expansion is accelerating due to dark energy.

Last verified on 19-07-2026

Explanation

• The reciprocal of bulk modulus is called compressibility.
• Formula: Compressibility = 1 / Bulk Modulus
• Bulk modulus measures resistance to compression.
• Symbol: β = 1/K.
• SI unit: Pa⁻¹ (per Pascal).
• Higher bulk modulus means lower compressibility

Last updated 18-07-2026 by NA

Explanation

• The SI unit of electric current is Ampere (A).
• Electric current measures the flow of electric charge.
• Defined using the elementary charge (e = 1.602176634 × 10⁻¹⁹ C).
• Named after: André-Marie Ampère (scientist).
• 1 Ampere = 1 Coulomb per second (1 A = 1 C/s).

Last verified on 08-06-2026

Explanation

• White goods are durable consumer goods, mainly large household electrical appliances.
• The term originally referred to appliances that were usually finished in white enamel.
• These products are designed for long-term household use.
• Examples: Refrigerator, Washing Machine, Air Conditioner, Dishwasher, Deep Freezer

Additional information:

• Brown goods include entertainment electronics such as TVs, radios, and audio systems.

Last verified on 18-07-2026

Explanation

• The speed of sound is maximum in solids 
• Because particles are tightly packed, allowing faster vibration transfer.
• In iron, sound travels around 5120 m/s,
• Much faster than in air (343 m/s) or water (1482 m/s).

Last updated 17 july 2026 by NA

Explanation

• Surface tension prevents water from penetrating waterproof materials.

Additional information 

• Friction: Force that opposes the motion between two surfaces in contact.
• Adhesion: Attraction between molecules of different substances.
• Gravity: Force that pulls objects toward the Earth

Last updated by NA on 16-07-2026

Explanation

• 24-karat (24K) gold is considered the "best"
• Purity: 99.9% pure gold.
• Color: Rich, deep, bright yellow.

Additional information

• 22K Gold: 91.7% pure gold. It is mixed with harder metals like silver or copper.
• 18K Gold: 75% pure gold. It is highly durable and excellent for diamond settings 
• Carat is the unit of measurement for the physical weight of diamonds/gold.

Last updated by NA on 16-07-2026