Explanation

• Concave lenses are also known as diverging lenses. 
• Shape: Thinner in the middle and thicker at the edges.
• Image: They produce smaller, upright, virtual images.
• Use: Often used in eyeglasses to correct myopia (nearsightedness). 

Last updated on 09-03-2026

Explanation

Citric acid occurs naturally in:

• Lemons,
• Limes,
• Pineapples,
• Grapefruits,
• Berries (not blueberries),
• Tomatoes,
• Broccoli,
• Carrots,
• and some varieties of Peppers.

Explanation

Blood has a pH level of around 7.3, which is closest to neutral (pH 7).

Explanation

The SI unit of volume is the cubic meter (m3), which is a derived unit.

1 m3 = 1 m • 1 m • 1 m.

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The SI unit of energy/work is the joule (J)

Explanation

• The Candela (cd) is the SI unit of luminous intensity.
• It is defined as the luminous intensity of a monochromatic source that emits light at a frequency of 540 x 10^12 Hz with a luminous efficiency of 683 lm/W.

Explanation

• The principal axis is a horizontal line that passes through the centre of the lens, perpendicular to its surface.
• It is the central axis around which the lens is symmetrical.

Explanation

A convex lens has either one or both of its surfaces curving outwards, that is, wider divergence from the plan at the center.

These lenses are used to correct long-sightedness (hypermetropia).

Explanation

• Ozone gas is a molecule made up of three oxygen atoms, with the chemical formula O3.
• This is different from ordinary oxygen, which has the chemical formula O2.

Explanation

The stratospheric ozone layer is Earth's “sunscreen”  protecting living things from too much ultraviolet radiation from the sun.

Oxygen layer in the atmosphere

Ozone protects us from the harmful ultraviolet radiation of the sun.

Ozone formula: O3

The ozone layer lies approximately 15-40 kilometers (10-25 miles) above the Earth's surface, in the stratosphere.

The ozone layer is depleting: Air pollution

ND17-7-2023

Explanation

• Replication is the process by which a cell makes an exact copy of its DNA before cell division, ensuring that the new cell receives a complete set of genetic instructions.
• This process is crucial for the transmission of genetic information from one generation of cells to the next.