Melanin is the natural pigment that gives colour to human skin, hair and the iris. It provides protection against
- A.Ultraviolet radiation
- B.Infrared radiation
- C.X-ray radiation
- D.Short wave radio radiation
Correct answer
Explanation
The correct answer is A, Ultraviolet radiation. Melanin absorbs the ultraviolet rays of sunlight and shields the DNA of skin cells from damage.
Melanin is made by cells called melanocytes in the lower layer of the epidermis. When the skin is exposed to sunlight, melanocytes produce more melanin, which is why skin tans. The pigment absorbs UV-A and UV-B and turns most of that energy into harmless heat, lowering the risk of sunburn and skin cancer. People with more melanin have darker skin and better natural protection, while albinism, the inability to make melanin, leaves skin very sensitive to the sun.
B is wrong because infrared is felt as heat and is not what melanin guards against.
C is wrong because X-rays pass through soft tissue and are stopped by dense materials such as lead, not by a skin pigment.
D is wrong because radio waves carry too little energy to harm skin cells.
Exam tip: melanin, made by melanocytes, protects against UV; its absence causes albinism.
Practice Questions
View allNephology is the branch of science that studies
- A.Kidneys
- B.Clouds
- C.Nerves
- D.Nebulae
Show answer
Nephology is the study of clouds, their formation, classification into types such as cirrus, cumulus and stratus, and their part in rainfall, and it is a branch of meteorology, the science of the atmosphere and the weather.
Read the full explanation →Herpetology is the branch of zoology dealing with the study of
- A.Molluscs
- B.Spiders
- C.Reptiles and amphibians
- D.Parasitic worms
Show answer
Herpetology is the study of reptiles such as snakes, lizards, crocodiles and turtles, together with amphibians such as frogs, toads and salamanders, and in India it includes the work on snake venom and antivenom at institutions that maintain snake parks.
Read the full explanation →Phycology, also known as algology, is the study of
- A.Algae
- B.Fungi
- C.Grasses
- D.Ferns
Show answer
Phycology, also called algology, is the study of algae, the simple photosynthetic organisms that range from the single-celled Chlamydomonas to the large brown seaweeds, and it covers their classification and their uses as food, fertiliser and a source of agar.
Read the full explanation →Cryogenics is the branch of physics that deals with
- A.Very high pressures
- B.Very low temperatures
- C.Crystal structures
- D.Cosmic rays
Show answer
Cryogenics deals with the production of very low temperatures and with the behaviour of materials at those temperatures, where liquefied gases such as liquid nitrogen, oxygen and hydrogen are used; it is applied in rocket engines with cryogenic upper stages, in superconducting magnets and in the preservation of biological material…
Read the full explanation →Speleology is the branch of science that studies
- A.Caves
- B.Clouds
- C.Glaciers
- D.Lakes
Show answer
Speleology is the exploration and scientific study of caves, their formation, the limestone features such as stalactites and stalagmites that develop in them, and the animal life adapted to permanent darkness.
Read the full explanation →