Consider the following statements regarding the structure of the atmosphere : I. The average height of the troposphere is higher nearer the poles than at the equator. II. The mesosphere contains the ozone layer. III. Radio waves transmitted from the Earth are reflected to the Earth by the ionosphere. IV. In the mesosphere, temperature decreases with an increase in altitude. Which of the statements given above are correct?
- A.I and II only
- B.II and III only
- C.III and IV only
- D.I, II, III and IV
Correct answer
Explanation
The correct answer is C, III and IV only. Statements III and IV describe the ionosphere and the mesosphere correctly, while I and II mix up facts about the troposphere and the ozone layer.
The troposphere is about 18 km thick over the equator and only about 8 km over the poles, because strong heating at the equator lifts air to greater heights. The ozone layer lies in the stratosphere, roughly 15 to 35 km up. In the mesosphere, from about 50 to 80 km, temperature falls with height and reaches about minus 100°C. Above it, the ionosphere holds charged particles that reflect radio waves back to the Earth, which makes long-distance radio possible.
A is wrong because statements I and II are both false. B is wrong because statement II is false: ozone is in the stratosphere. D is wrong because it includes the two false statements.
Exam tip: troposphere thickest at the equator, ozone in the stratosphere, radio waves bounce off the ionosphere.
Practice Questions
View allLoktak lake is situated in the State of
- A.Sikkim
- B.Manipur
- C.Odisha
- D.Mizoram
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Loktak Lake lies south of Imphal in Manipur and is the largest freshwater lake in North-East India. Loktak is famous for its phumdis, floating masses of soil, vegetation and decaying organic matter that drift on the water.
Read the full explanation →The formation of 'tors' on small rocky hills is associated with which among the following?
- A.Granite
- B.Limestone
- C.Alluvial
- D.Dolomite
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Tors are piles of rounded, weathered blocks standing on hilltops, and they form typically in granite. Granite cools deep underground and develops a network of joints, or cracks.
Read the full explanation →Which one of the following statements is NOT correct ?
- A.Bokaro steel plant is located in Damodar river basin
- B.Jamshedpur steel plant is located on the confluence of Damodar and Barakar
- C.Salem steel plant is located on the bank of Kaveri River
- D.Bhilai steel plant obtains water from Tandula reservoir
Show answer
Jamshedpur stands at the meeting point of the Subarnarekha and Kharkai rivers, not the Damodar and Barakar. Jamsetji Tata chose Sakchi, later named Jamshedpur, and the Tata Iron and Steel Company began production there in 1912.
Read the full explanation →Which of the following is/are warm ocean current(s) ? 1. Alaska Current 2. Agulhas Current 3. Falkland Current 4. West Australian Current Select the answer using the code given below :
- A.1 only
- B.1 and 2
- C.3 and 4
- D.4 only
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The Alaska Current and the Agulhas Current carry warm water, while the Falkland and West Australian currents are cold. A useful rule is that currents flowing from the tropics towards the poles are warm and those flowing from high latitudes towards the equator are cold.
Read the full explanation →Consider the following statements regarding the nature of rocks : I. Rocks are aggregates of one or more minerals. II. Granite is softer than soapstone. III. Gabbro is black and quartzite can be milky white. IV. Sedimentary rocks are related to foliation. Which of the statements given above are not correct ?
- A.I and II
- B.I and III
- C.II and IV
- D.II and III
Show answer
Granite is far harder than soapstone, and foliation is a feature of metamorphic rocks, not sedimentary ones, so these two statements are wrong.
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