Science And Technology - MCQ Online Test (4) UPSC General MCQs & solutions

The outer color (silvery) will reflect most of
radiation, while the black color inside will absorb anything passing through outer layer. White color will reflect more and absorbs less.

This relative mobility of electrons within a
material is known as electric conductivity.
Conductivity is determined by the types of atoms in a material (the number of protons in each atom’s nucleus, determining its chemical identity) and how the atoms are linked together with one another.
Materials with high electron mobility (many free electrons) are called conductors, while materials with low electron mobility (few or no free electrons) are called insulators.
It must be understood that not all conductive
materials have the same level of conductivity, and not all insulators are equally resistant to electron
motion.

Heat can cause a change in body’s
temperature by changing the internal energy of the body. Internal energy of a body is the total energy (Kinetic and potential) of its molecules. Heat energy
is produced at the expense of mechanical energy and vice versa. Ex: - Rub your palms vigorously, palm becomes warmer. Heat is measurable quantity it is expressed in calorie or Joule.

An artificial satellite moving round the Earth in a circular orbit possesses an acceleration which is "constant" in magnitude but "changing in direction".
An artificial satellite revolves round the earth under centripetal acceleration. By the launch rocket, immediately before the satellite is established in the predetermined orbit, the speed given to it is 30, 000
km/hr. The speed must be great enough so gravity doesn't bring the satellite back to Earth, but not so great that the satellite escapes gravity out into space.
This means that the speed, which is provided by the rocket is the source of the centrifugal force, and the attraction of the earth holds it from moving away from
this centrifugal force. In this question Option D is correct answer

A cryogenic rocket engine is a rocket engine that uses a cryogenic fuel or oxidizer, that is, its fuel or oxidizer (or both) are gases liquefied and stored at very low temperatures. Rocket engines need high mass flow rate of both oxidizer and fuel to generate a sufficient thrust. At that time oxygen and low molecular weight hydrocarbons were used as oxidizer and fuel pair. At room temperature and pressure, both are in gaseous state. Hypothetically, if propellants had been stored as pressurized gases, the size and mass of fuel tanks themselves would severely decrease rocket efficiency. Therefore, to get the required mass flow rate, the only option was to cool the propellants down to cryogenic temperatures (below −183 °C [90 K], −253 °C [20 K]), converting them to liquid form. Hence, all cryogenic rocket engines are also, by definition, either liquid-propellant rocket engines or hybrid rocket engines.

In the process of photosynthesis, the phosphorylation of ADP to form ATP using the energy of sunlight is called photo phosphorylation. Only two sources of energy are available to living organisms: sunlight and reduction-oxidation (redox) reactions. All organisms produce ATP, which is the universal energy currency of life. This involves photolysis of water and a continuous unidirectional flow of electron from water to PS. In photo phosphorylation, light energy is used to create a high-energy electron donor and a lowerenergy electron acceptor. Electrons then move spontaneously from donor to acceptor through an electron transport chain.

White blood cells are also referred to as WBCs or leukocytes. They are the cells that make up the majority of the immune system, which is the part of the body that protects itself against foreign substances and various types of infections. Leukocytes are made in the bone marrow from multipotent cells called hematopoietic stem cells. Leukocytes exist in all parts of the body, including the connective tissue, lymph system, and the bloodstream. There are five different types of white

Viruses lie around our environment all of the time just waiting for a host cell to come along. They can enter us through the nose, mouth or breaks in
the skin. Viruses are spread (transmitted) in various ways. Some are swallowed, some are inhaled, and some are spread by the bites of insects, such as mosquitoes, certain biting flies, or ticks. Some are spread sexually or during transfusion of contaminated blood.

Dietary fiber or roughage is the indigestible portion of food derived from plants. It has two main components:
 Soluble fiber, which dissolves in water, is readily fermented in the colon into gases and physiologically active byproducts, and can
be prebiotic and viscous.
 Insoluble fiber, which does not dissolve in water, is metabolically inert and provides bulking, or it can be prebiotic and metabolically ferment in the large intestine. Bulking fibers absorb water as they move through the digestive system, easing defecation

Vitamin C cannot be made by the human body and so is an essential component of the diet. It is needed for the health and repair of various tissues in your body, including skin, bone, teeth and cartilage. Persistent lack of vitamin C in your diet can lead to a condition called scurvy. Symptoms of scurvy include easy bruising, easy bleeding and joint and muscle pains. Vitamin C deficiency can be treated with supplements of vitamin C and a diet rich in vitamin C.

Vitamin A Deficiency Symptoms. The
main symptom of vitamin A deficiency is vision loss and blindness. Vision loss often begins as a problem adjusting to seeing in the dark, or night blindness

A compound is made when atoms of different elements join together by chemical bonds. This means that ... Water molecule, Water -two hydrogen atoms and one oxygen atom joined together.

It is a soft, silver-white metal belonging to
the alkali metal group of chemical elements.
Under standard conditions, it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly reactive and flammable.

Photographic fixer is a mix of chemicals used in the final step in the photographic processing of film or paper. The fixer stabilises the image, removing the unexposed silver halide remaining on the photographic film or photographic paper, leaving behind the reduced metallic silver that forms the image. By fixation, the film or paper is insensitive to further action by light. Without fixing, the remaining silver halide would darken and cause fogging of the image. Fixation is commonly achieved by treating the film or paper with a solution of thiosulfate salt. Popular salts are sodium thiosulfate—commonly called hypo—
and ammonium thiosulfate

Thirteen vitamins are universally recognized at present. Vitamins are classified by their biological and chemical activity, not their structure. An organic chemical compound (or related set of compounds) is called a vitamin when
the organism cannot synthesize the compound in sufficient quantities, and it must be obtained through the diet; thus, the term "vitamin" is conditional upon the circumstances and the particular organism.

All organisms on Earth are carbon-based life forms, meaning that most of their complex molecules are made up of carbon bonded to other elements. the atoms of carbon in human body were once part of carbon dioxide in the air! Carbon atoms end up in human body, and in other life forms, thanks to the second stage of photosynthesis, known as the Calvin
cycle (or the light-independent reactions).

During the process of photosynthesis, light
penetrates the cell and passes into the chloroplast. The light energy is intercepted by chlorophyll molecules on the granal stacks. Some of the light energy is converted to chemical energy. During this process, a phosphate is added to a molecule to cause the formation of ATP.
The third phosphate chemical bond contains the new chemical energy. The ATP then provides energy to some of the other photosynthetic reactions that are causing the conversion of CO2 into sugars.

Black diamond or carbonado is toughest form of natural diamond. It is impure form of polycrystalline diamond consisting of diamond graphite and amorphous carbon, with minor crystalline precipitates filling pores and occasional reduced metal inclusions.
So, 1 is correct

Graphite on heating gives daimond but not vice versa .so 2 is wrong

The complete hydrolysis of proteins yield about 20 different aminoacids. It was concluded that proteins are made up of only amino acids.

Amino acids are chemical compounds that contain both acidic carboxy and basic amino groups. The amino acids of a protein are united to one another by their respective carboxyl and amino groups, forming a peptide bond and with repetition it is called as polypeptide chain. All are correct

Methamphetamine is a strong central nervous system (CNS) stimulant that is mainly used as a recreational drug and less commonly as a treatment for attention deficit hyperactivity disorder and obesity.
Ephedrine is Methamphetamine analogue but not the same. Both are recreational drugs.

Lactic acid is formed and accumulated in the muscle under conditions of high energy demand, rapid fluctuations of the energy requirement and insufficient supply of oxygen. During intense exercise sustained to fatigue muscle ph decreases to 6.4-6.6

Congenital disease is birth defect or anomaly is a condition existing at or before birth regardless of cause involves in a developing foetus

Antidepressants are used for treating depression like syndromes, they work by removing certain chemicals from brain like neurotransmitters so 1 is correct Antipyretics like aspirin is used during fever to reduce temp. Anything described as antipyretic works against a fever.
So both are correct.

Tea stimulates nervous system. Green tea is good for digestive system, and it contains polyphenols, catechins. C is correct.

They are least subatomic particles they are least interactive so need large detector to have a solar interact .not difficult to detect but to interact we need a large detector so third statement is incorrect.

An ultrasound scan is a medical test that uses high-frequency sound waves to capture live images from the inside of your body. The technology is similar to that used by sonar and radar, which help the military detect planes and ships. An ultrasound allows your doctor to see problems with organs, vessels, and tissues—without needing to make an incision..Unlike other imaging techniques, ultrasound uses no radiation, so it is the preferred method for viewing a developing fetus during pregnancy. Ultrasound is also known as sonography.

Because kinetic energy of parachute was affected by the mass attached

Both due to refraction. Refraction is the bending of a wave when it enters a medium where its speed is different. The refraction of light when it passes from a fast medium to a slow medium bends the light ray toward the normal to the boundary between the two
media.