UPSC Civil Services GK Questions 2026

The molecules of the atmosphere are much smaller than the wavelength of visible light, and such particles scatter short wavelengths far more strongly than long ones.

In hypermetropia the eye lens is too weak or the eyeball is too short, so rays from a nearby object are not converged enough and the image falls behind the retina.

The retina carries two kinds of photoreceptor. Cone cells need reasonably bright light to work and respond selectively to different wavelengths, so they give us the sensation of colour; when the cones are defective a person is colour blind.

The refractive index of a transparent medium is not the same for every colour; it rises as the wavelength falls.

Two steps are needed. First, the focal length must be converted to metres: 50 centimetres is 0.5 metre.

The power of a lens measures how strongly it converges or diverges light, and it is defined as one divided by the focal length expressed in metres.

The least distance of distinct vision, also called the near point, is the smallest distance at which an object can be held and still be seen clearly without strain.

The iris is the coloured ring of muscle lying just behind the cornea. By contracting and relaxing it makes the central opening, the pupil, smaller in bright light and larger in dim light, and in this way it regulates how much light falls on the retina.

A soap film is extremely thin, and light reflected from its front surface meets light reflected from its back surface.

The cornea is the thin, transparent, slightly bulging membrane that forms the front surface of the eyeball, and light must pass through it before reaching anything else.

Myopia, or short-sightedness, is the defect in which nearby objects are seen clearly but distant objects look blurred. It arises either because the eye lens has become too converging, that is its focal length is too short, or because the eyeball has grown too long from front to back.

The CITES Secretariat is based at Geneva in Switzerland and is administered under the United Nations Environment Programme; it services the Conference of the Parties, maintains the appendices and advises member states on permits and enforcement.

This large land snail is native to East Africa and reached India long ago, probably through the trade in ornamental plants and shells.

The Wild Life (Protection) Amendment Act of 2022 brought the parent Act into line with India obligations under CITES, reorganised its schedules and for the first time inserted an express power allowing the Central Government to regulate or prohibit the import, trade, possession and proliferation of invasive alien species.

Neem is native to the Indian subcontinent, so by definition it cannot be an alien species here, however widely it has been planted; a species is alien only outside its natural range.

The mongoose is a protected animal under the Wild Life (Protection) Act, yet its hair was being used to make artists brushes, and Operation Clean Art was the Bureau first country-wide operation directed at a single wildlife article, ending with large seizures of brushes and raw hair.

Zygogramma bicolorata is a leaf-feeding beetle from Mexico, the native region of Parthenium hysterophorus, and it was introduced in India as a biological control agent because its grubs and adults strip the weed of leaves and check its seed production.

Parthenium hysterophorus reached India from tropical America, reportedly with imported wheat, and spread rapidly over waste ground, roadsides and fallow fields.

The Wildlife Crime Control Bureau is a multi-disciplinary statutory body created in 2007 under section 38Z of the Wild Life (Protection) Act, 1972.

CITES sorts species into appendices according to how badly trade threatens them.