41.In plant-water relationships, symbol YW is used to represent ______:
[A] Solute potential
[B] Osmotic pressure
[C] Osmosis
[D] Water potential
Answer: D [Water potential]
Notes:
Water potential is the potential energy of water per unit volume relative to pure water in reference conditions. Hence, it quantifies the tendency of water to move from one area to another due to osmosis, gravity, mechanical pressure, or matrix effects such as surface tension. Water potential is typically expressed in potential energy per unit volume and very often is represented by the famous Greek letter.
42.What is the maximum number of electrons that can be present in a shell represented by shell number ‘n’?
[A] 2n
[B] 2n2
[C] n
[D] n2
Answer: B [2n2]
Notes:
An electron shell, or a principal energy level, may be thought of as an orbit followed by electrons around an atom’s nucleus. Each shell can contain only a fixed number of electrons: The first shell can hold up to two electrons, the second shell can hold up to eight (2 + 6) electrons, the third shell can hold up to 18 (2 + 6 + 10) and so on. The general formula is that the nth shell can in principle hold up to 2(n2) electrons.
43.Which of the following metals is the most reactive metal?
[A] Copper
[B] Calcium
[C] Iron
[D] Zinc
Answer: B [Calcium]
Notes:
Among the given options, Calcium is the most reactive since it has the greatest tendency to lose electrons and form positive ions. However, calcium is less reactive than Potassium and Sodium.
44.What is the water found below water table called?
[A] Water cycle
[B] Water table
[C] Ground water
[D] Aquifer
Answer: C [Ground water]
Notes:
Water table, also called Groundwater Table, upper level of an underground surface in which the soil or rocks are permanently saturated with water. The water table separates the ground water zone that lies below it from the capillary fringe, or zone of aeration, that lies above it.
45.Who is the only scientist in the world to have won the Nobel prize in Chemistry twice?
[A] Linus Carl Pauling
[B] Roger D. Kornberg
[C] Madame Curie
[D] Frederick Sanger
Answer: D [Frederick Sanger]
Notes:
• Sanger is the only person to have been awarded the Nobel Prize in Chemistry twice. (a) He is one of only four two-time Nobel laureates. (b) The other three were
• Marie Curie (Physics, 1903 and Chemistry, 1911)
• Linus Pauling (Chemistry, 1954 and Peace, 1962)
• John Bardeen (twice Physics, 1956 and 1972).
46.Which of the following is natural fiber?
[A] Silk
[B] Rayon
[C] Nylon
[D] Polyester
Answer: A [Silk]
Notes:
Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from the cocoons of the larvae of the mulberry silkworm Bombyx mori reared in captivity (sericulture).
47.Action and reaction _:
[A] always act on same body
[B] are equal in magnitude
[C] are in same direction
[D] always act independently
Answer: B [are equal in magnitude]
Notes:
According to Newton’s third law of motion, to every action there is an equal and opposite reaction’. It indicates that when one object exerts a force on another object, the second object instantaneously exerts a force back on the first object. These two forces are always equal in magnitude, but opposite in direction.
48.Which of the following is the unit of perceived loudness of sound ?
[A] Decibel
[B] Sone
[C] Hertz
[D] Phon
Answer: B [Sone]
Notes:
Perceived loudness of sound is a psycho-acoustic quantity that depends on sound pressure level, the frequency spectrum, and the time behavior of the sound. The sone is a unit of perceived loudness that was proposed by Stanley Smith Stevens in 1936.Being a unit of how loud a sound is perceived, the sone scale of loudness is based on data obtained from subjects who were asked to judge the loudness of pure tones and noise. One sone is arbitrarily set equal to the loudness of a 1,000-hertz tone at a sound level of 40 decibels.
49.Transition ions absorb light in :
[A] infrared region
[B] ultraviolet region
[C] microwave region
[D] visible region
Answer: D [visible region]
Notes:
Transition metal ions which are mostly coloured except for zinc and scandium have an incomplete set of 3d electrons. Changes in the energy of these electrons correspond to the energy of visible light. The absorption of visible light by these ions lend colour to gems.
50.Which of the following is a semiconductor__?
[A] silver
[B] copper
[C] Glass
[D] Silicon
Answer: D [silicon]
Notes:
Silicon is the most used semiconductor for discrete devices and integrated circuits. Its combination of low raw material cost, relatively simple processing, and a useful temperature range makes it currently the best compromise among the various competing materials. Germanium (Ge) was a widely used early semiconductor material but its thermal sensitivity makes it less useful than silicon.