Explanation

• The SI unit of energy is the Joule (J).
• It is the unit of energy, work, and heat.

Additional information:

• 1 Joule (J) = 1 Newton × 1 meter
• Calorie – 1 cal = 4.184 J
• Kilowatt-hour (kWh) – 1 kWh = 3.6 × 10⁶ J
• Electronvolt (eV) – 1 eV ≈ 1.602 × 10⁻¹⁹ J
• Erg (CGS unit) – 1 erg = 10⁻⁷ J

Last verified on 17-01-2026

Explanation

• Venus is the brightest planet in the night sky.
• Due to its thick cloud cover that reflects sunlight strongly.
• It is often called the “Evening Star” or “Morning Star.”

Additional information:

• Distance from Sun: ~108 million km
• Diameter: 12,104 km
• Orbital Period: 225 Earth days
• Atmosphere: Thick CO₂ clouds, very reflective

Last verified on 15-01-2026

Explanation

• Cause: Mainly due to sulfur dioxide (SO₂) released from burning fossil fuels like coal and oil.
• Effect: SO₂ reacts with water vapor in the atmosphere to form sulfuric acid, causing acid rain.

Last verified on 08-02-2026

Explanation

• The part of the eye that controls the amount of light entering is the Iris.
• It adjusts the size of the pupil according to light intensity.
• In bright light, it reduces light entry; in dim light, it allows more light in.
• This process protects the retina and helps clear vision.

Last verified on 17-05-2026

Explanation

• 1 Nanometer (nm) = 10⁻⁹ m (1 × 10⁻⁹ m)

Additional information:

• 1 Kilometer (km) = 10³ m
• 1 Meter (m) = 10⁰ m
• 1 Millimeter (mm) = 10⁻³ m
• 1 Micrometer (µm) = 10⁻⁶ m

Last verified on 06-07-2026

Explanation

• The modern periodic table arranges elements in order of increasing atomic number.
• The atomic number is the number of protons present in the nucleus of an atom.
• Elements with similar chemical properties are placed in the same group (vertical column).
• The modern periodic law was established by Henry Moseley.

Last verified on 12-10-2026

Explanation

• A neutron has no electric charge, so it is electrically neutral.

Additional information:

• A proton has a positive charge (+1).
• An electron has a negative charge (−1).

Last verified on 07-10-2026

Explanation

• The atomic number of hydrogen is 1.
• It is the first element on the periodic table. 
• Named by: Antoine Lavoisier (1783)
• Atomic mass: 1.00784 u
• Appearance: Colorless gas
• Symbol: H
• Protons: 1
• Electrons: 1

Last updated 26-07-2026 by NA

Explanation

• Velocity is a vector quantity. 
• A vector quantity has both magnitude and direction.
• Velocity, which describes the rate of change of position in a specific direction.
• It needs both a magnitude (speed) and a direction to be fully defined. 
• Vector Quantities: Velocity, momentum, torque, acceleration.
• Scalar Quantities: Work, distance, speed, mass.

Last verified on 12-10-2026

Explanation

• Mars is known as the Red Planet due to its reddish appearance.
• Its surface contains iron oxide (rust) which gives it a red color.
• It is the 4th planet from the Sun in the solar system.
• Mars has two small moons: Phobos and Deimos.
• Mars is often called the “planet of future exploration”.

Last verified on 12-06-2026