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11. Discuss briefly the following :

       (c) Ultraviolet B

Ultraviolet- B The part of ultraviolet radiation having a wavelength of 280-320 nm. UV-B is harmful to organisms. The ozone layer in the stratosphere absorbs 50% of total UV-B. Due to depletion of ozone, mostly UV-B radiations reach the Earth. In humans, UV radiation causes snow blindness, cataract, skin cancer, skin ageing, mutations etc. 

11. Discuss briefly the following :

     (b) Catalytic converter

Catalytic converter Catalytic converter refers to a device containing platinum, palladium and rhodium that is fitted in the automobiles. The major functions of catalytic converters in the automobile are 1. Complete oxidation of unburnt hydrocarbons 2. Oxidation of carbon monoxide into carbon dioxide 3. Conversion of nitrogen oxides into nitrogen  While using catalytic converters, we must not...

11. Discuss briefly the following :

     (a) Greenhouse gases 

Greenhouse gases- The gases which cause the greenhouse effect are called greenhouse gases e.g. carbon dioxide, methane, chlorofluorocarbons, nitrous oxide etc. Greenhouse gases allow long wave radiations to enter into the atmosphere but do not let them leave, so these radiations remain trapped in the atmosphere. This causes the greenhouse effect. This is similar to the effect of glass walls in...

10. What initiatives were taken for reducing vehicular air pollution in Delhi? Has air quality improved in Delhi?

Delhi is considered to be one of the most polluted cities. The major reasons of Delhi being polluted include increased fossil fuel consumption, increased number of industries etc. Government has taken several steps in order to minimise the vehicular air pollution. Some of these steps are as follows:  1. Introduction of CNG- The supreme court of India in the year 2006, in order to reduce the air...

9. Discuss briefly the following:

    (c) Municipal solid wastes

The solid waste generated from schools, offices, homes, stores etc is known as municipal solid wastes. The municipal solid waste includes glass, food articles, plastics, stationery, rubber, leather, textiles etc. The municipal solid waste is necessary to dispose of as it acts as a breeding site for mosquitoes thus leading to diseases like dengue, malaria etc. The methods used for safe disposal...

9. Discuss briefly the following:

    (b) Defunct ships and e-wastes 

Defunct ships and e-wastes- The dead ships which are not in use are called defunct ships. Defunct ships can be broken down for scrap metal in some countries. Defunct ships can act as a source of heavy metals such as asbestos, lead, mercury etc. E- wastes also called electronic wastes include waste products generated from electronic goods such as computers, televisions, refrigerators etc. Such...

9. Discuss briefly the following:

    (a) Radioactive wastes

Radioactive Wastes-  These waste products include nonusable discards that possess radioactivity. Rdioactive wastes are of three types- 1. Wastes with low-level radioactivity- Include coolant water of atomic reactors, pond water for cooling spent fuel in reactors etc. They emit very small amounts of radioactivity. Irradiation centres, radiotherapy units and laboratories also produce wastes with...

8. What measures, as an individual, would you take to reduce environmental pollution?

The following measures can be taken to reduce environmental pollution 1. Planting more number of trees 2. we can reduce the use of fossil fuels by not using our own vehicles to travel short distances.  3. We should use clean fuel such as CNG in our cars which environment-friendly as well as pocket-friendly. 4. We must segregate the wastes into biodegradable and non-biodegradable waste products....

7. Discuss the role of women and communities in protection and conservation of forests.

The role of women and communities in the protection and conservation of forests can be understood by following two case studies: 1. Bishnoi community- The Bishnoi community in Bishnoi village of Rajasthan fought with the king and his army for the protection of trees. Amrita Devi a woman of Bishnoi lead this movement and with her daughter and hundreds of other members of her community, embraced...

6. Why does ozone hole form over Antarctica? How will enhanced ultraviolet radiation affect us?

The countries like USA, Japan, and other European countries, emit a lot of ozone-depleting substances such as These chemicals are released in the stratosphere and they drift towards poles before the onset of winters. During winter, ice clouds are formed over Antarctica with no sunrise. It catalyses the release of Cl from CFCs. During springs, the Cl reacts with ozone and convert it into free...

5. Match the items given in column A and B:

Column A Column B
a.Catalytic converter i. Particulate matter
b.Electrostatic precipitator ii. Carbon monoxide and nitrogen oxides
c.Earmuffs iii. High noise level
d. Landfills iv. Solid Wastes


  The correct matching is as follows: Column A Column B Catalytic converter Carbon monoxide and nitrogen oxides Electrostatic precipitator Particulate matter Earmuffs High noise level Landfills  Solid Wastes      

4. Write critical notes on the following:  

    (c) Groundwater depletion and ways for its replenishment

Groundwater depletion and ways of its replenishment-  Groundwater is being pumped out at an enormous rate for its use in agricultural and urban areas resulting in the fall of the water table by 10 m to 30m and depletion of groundwater.  Ways of replenishment of groundwater 1. Rainwater harvesting- The rainwater can be preserved and through this, groundwater is recharged.  2. Sprinkler and...

4. Write critical notes on the following:

    (b) Biological magnification 

Biological magnification- It refers to the increase in the concentration of a persistent chemical with the rise in trophic level. The chemical becomes hazardous when its concentration becomes very high. For example, a DDT concentration of 0.003 ppb becomes 0.003 ppm in phytoplankton, 0.04 ppm in zooplankton, 0.5 ppm in small fish, 2.0 ppm in larger fish and 5 ppm in fish-eating birds.    

4. Write critical notes on the following:

     (a) Eutrophication 

Eutrophication- The term eutrophication is used to refer to the excessive growth of algae, plants and animals in water bodies due to the nutrient enrichment of the water body with nitrogen and phosphorous. Eutrophication can be natural or accelerated. In the case of natural eutrophication, natural ageing causes nutrient enrichment of the water body. This is a slow process that is not detectable...

3. Discuss the causes and effects of global warming. What measures need to be taken to control global warming?

Global warming- The rise in the mean temperature of the earth is called global warming. Causes of global warming- Global warming is mainly caused due to the increased amounts of greenhouse gases in the atmosphere. These gases allow long wave radiations to enter into the atmosphere but do not let them leave, so these radiations remain trapped in the atmosphere and cause the mean temperature to...

2. List all the wastes that you generate, at home, school or during your trips to other places. Could you very easily reduce the generation of these wastes? Which would be difficult or rather impossible to reduce?

In our daily life, we generate a lot of waste at our home, schools, during trips etc. 1. Waste generated at homes- waste paper, old clothes, leather articles, broken crockery, cartons, food leftovers, kitchen wastes etc.  2. Waste generated in schools- paper, discarded pencils, pen refills, cardboards, polythene bags, fruit peels, wrappers etc.  3. Waste generated during trips- papers, plastic...

1. What are the various constituents of domestic sewage? Discuss the effects of sewage discharge on a river.

Domestic sewage refers to the wastewater coming from toilets, kitchen and washings which is passed into sewer systems. Domestic sewage contains fibrous matter, grit, colloidal particles, faecal matter, small sized food leftovers, pathogens, nitrates, phosphates and other salts etc. The effects of sewage discharge on a river 1. Sewage discharge causes a rise in BOD or biological oxygen demand...