SSC CGL -Science Questions 4 September 2016

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Q1.Green House Effect' means

1) Pollution in houses in tropical region
2) Prevention of ultra-violet radiation by the ozone layer
3) Trapping of solar energy due to atmospheric gases
4) Damage to green painted buildings

Explanation -

The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without its atmosphere.

Earth’s natural greenhouse effect is critical to supporting life. Human activities, mainly the burning of fossil fuels and clearing of forests, have strengthened the greenhouse effect and caused global warming.

By their percentage contribution to the greenhouse effect on Earth the four major gases are

·         water vapor, 36–70%

·         carbon dioxide, 9–26%

·         methane, 4–9%

·         ozone, 3–7%

Protocols on global warming

The Kyoto Protocol 

The Kyoto Protocol was adopted in Kyoto, Japan on 11 December 1997 and entered into force on 16 February 2005. 

There are currently 192 parties (Canada withdrew effective December 2012) to the Protocol.

The Kyoto Protocol is an international treaty which extends the 1992 United Nations Framework Convention on Climate Change.

The Kyoto Protocol applies to the six greenhouse gases -

1.Carbon dioxide (CO2), 

2.Methane (CH4), 

3.Nitrous oxide (N2O), 

4.Hydrofluorocarbons (HFCs) 

5.Perfluorocarbons (PFCs) 

6.Sulphur hexafluoride (SF6).

Q.2 Addition of suitable impurities into semiconductor, is called
1) Doping
2) Mixing
3) Forming
4) Diluting

Explanation –

What is Doping ?

Intentionally introducing impurities into an extremely pure semiconductor to change its electrical properties.

Conductors -   a conductor is an object or type of material that allows the flow of an electrical current in one or more directions. Materials made of metal are common electricalconductors.

very low values of resistivity, This low value allows them to easily pass an electrical.

Good examples conductors are generally metals such as Silver ,Copper, Aluminium etc.

Is Carbon conduct electricity because it is Non-Metal?

Ans- Carbon by its own  does not conduct electricity, but its allotrope graphite conducts electricity . This is because graphite has a “free” electron in its outer shell that allows it to conductsome electricity. 

Semiconductor Basics

They have electrical properties somewhere in the middle, between those of a “conductor” and an “insulator”. 

They are not good conductors nor good insulators (hence their name “semi”-conductors). They have very few “free electrons” because their atoms are closely grouped together in a crystalline pattern called a “crystal lattice” but electrons are still able to flow, but only under special conditions.

Examples - silicon (Si), germanium (Ge) and gallium arsenide (GaAs).

Silicon and Germanium are classed as intrinsic semiconductors, that is they are chemically pure, as the doped silicon is no longer pure.

Note-  Silicon is most commonly used semiconductor, it has four valence electrons in its outermost shell.

Insulators

They are the exact opposite of conductors.

3.Kyoto Protocol is associated with
1) Species conservation
2) Climate change
3) Wetland Conservation
4) Medicinal plants

4.Meibomian glands are located in


1) Eye
2) Ear
3) Nose
4) Skin 

Explanation –

The Meibomian glands (often written with a small m, and also called tarsal glands) are a holocrine type of exocrine glands, at the rim of the eyelids inside the tarsal plate, responsible for the supply of meibum, an oily substance that prevents evaporation of the eye's tear film. Meibum prevents tear spillage onto the cheek, trapping tears between the oiled edge and the eyeball, and makes the closed lids airtight.

Brunner's glands (or duodenal glands).

The main function of these glands is to produce a mucus-rich alkaline secretion (containing bicarbonate) in order to:

·         protect the duodenum from the acidic content of chyme (which is introduced into the duodenum from the stomach)

·         provide an alkaline condition for the intestinal enzymes to be active, thus enabling absorption to take place

·         lubricate the intestinal walls

Sebaceous glands 

Sebaceous glands are microscopic exocrine glands in the skin that secrete an oily or waxy matter, called sebum.

In humans, they occur in the greatest number on the face and scalp, but also on all parts of the skin except the palms of the hands and soles of the feet.

Sebum, secreted by the sebaceous gland in humans, is primarily composed of triglycerides (≈41%), wax esters (≈26%), squalene (≈12%), and free fatty acids (≈16%).

5.Arsenic problem in India is primarily due to

1) Overexploitation of coal in Bihar and Bengal
2) Overexploitation of arsenopyrite in the hinterland
3) Overexploitation of ground water in the affected areas
4) Overexploitation of surface water in the affected areas

Arsenic contamination in groundwater in the Ganga- Brahmaputra fluvial plains in India and Padma-Meghna fluvial plains in Bangladesh and its consequences to the human health have been reported as one of the world’s biggest natural groundwater calamities to the mankind. In India, seven states namely- West Bengal, Jharkhand, Bihar, Uttar Pradesh in the flood plain of the Ganga River; Assam and Manipur in the flood plain of the Brahamaputra and Imphal rivers and Rajnandgaon village in Chhattisgarh state have so far been reported affected by Arsenic contamination in groundwater above the permissible limit of 10 µg/L.

6.Which of the following vitamins are water soluble?

1) Vit. A & Vit. B
2) Vit. B & Vit. C
3) Vit. C & Vit. D
4) Vit. A & Vit. K

The two different types of vitamins are fat-soluble vitamins and water-soluble vitamins. Fat-soluble vitamins — vitamins A, D, E and K — dissolve in fat before they are absorbed in the bloodstream to carry out their functions. Excesses of these vitamins are stored in the liver, and are not needed every day in the diet

7.Besides CO2, the other green house gas is

Options:

1) CH4
2) N2
3) Ar
4) O2