Explanation

• Citric acid is a natural preservative found in many fruits, particularly in citrus fruits like lemons, oranges, and grapefruits.
• It's responsible for their sour taste and is also used as a food additive.
• Other fruits like mangoes, grapes, and strawberries also contain citric acid, although in smaller amounts.
• The presence of citric acid gives these fruits their characteristic sour taste.

Last verified on 16-03-2026

Explanation

• When light is focused in front of the retina, it creates a blurred image, indicating nearsightedness (myopia).
• This occurs because the eyeball is too long or the cornea is too steep.
• It causing light to focus before reaching the retina.

Last verified on 16-03-2026

Explanation

• Bases are substances that have a soapy or slippery feel when touched.
• This property occurs because bases react with oils on the skin, giving a soap-like texture.
• Many bases also turn red litmus paper blue in chemical tests.
• Common bases are used in cleaning agents, soaps, and detergents.

Last verified on 16-03-2026

Explanation

• The iris is the colored part of the eye that controls the size of the pupil.
• By adjusting the pupil size, it regulates the amount of light entering the eye, just like a camera diaphragm.
• Pupil dilation occurs in low light, letting in more light.
• Pupil contraction occurs in bright light, protecting the retina from damage.

Last verified on 15-03-2026

Explanation

• According to the Kinetic Molecular Theory, faster gas particles hit container walls more often.
• More frequent and stronger collisions increase the pressure.
• Higher temperature → higher particle speed → higher pressure.
• Pressure depends on number of collisions of gas molecules with container walls.
• Unit of gas pressure: Pascal (Pa).

Last verified on 13-03-2026

Explanation

• Respiration (breathing) is mainly controlled automatically by the brain’s respiratory center in the medulla oblongata.
• Normally, breathing occurs without conscious control, so it is an involuntary process.
• When a person cannot control breathing voluntarily (e.g., during sleep or unconsciousness), the body automatically continues respiration.

Last verified on 13-03-2026

Explanation

• 1 kilogram (Kg) = 1000 grams (g)
• So, 0.2 Kg = 0.2 × 1000 g = 200 g
• Mass is a measure of matter in an object.

Last verified on 13-03-2026

Explanation

• Acceleration is not a base quantity.

The base quantities are:

• Length (L)
• Mass (M)
• Time (T)

Last verified on 13-03-2026

Explanation

• A barometer measures atmospheric (air) pressure.
• It helps in weather forecasting, detecting storms, and studying climate changes.
• Two common types of barometers: mercury barometer and aneroid barometer.

Last verified on 13-03-2026

Explanation

• The ozone layer is a part of the Earth’s stratosphere that absorbs most of the Sun’s harmful ultraviolet (UV) radiation.
• Without it, UV rays could cause skin cancer, cataracts, and environmental damage.
• It is found approximately 15–35 km above Earth’s surface.

Last verified on 13-03-2026