Consider the following statements : 1. In a seismograph, P waves are recorded earlier than S waves. 2. In P waves, the individual particles vibrate to and fro in the direction of wave propagation whereas in S waves, the particles vibrate up and down at right angles to the direction of wave propagation. Which of the statements given above is/are correct?
- A.1 only
- B.2 only
- C.Both 1 and 2
- D.Neither 1 nor 2
Correct answer
Explanation
The correct answer is C, Both 1 and 2. P waves are the fastest seismic waves and reach a seismograph first, and they move particles along the direction of travel, while S waves move them at right angles to it.
An earthquake sends out two kinds of body waves. Primary or P waves are longitudinal, like sound: they push and pull the rock back and forth in the direction the wave moves, and they can pass through solids, liquids and gases. Secondary or S waves are transverse: the particles move up and down or side to side, perpendicular to the direction of travel, and they cannot pass through liquids. That is why S waves vanish in a shadow zone beyond about 103° from the epicentre, which told scientists that the outer core is liquid. Surface waves arrive last and do the most damage.
A is wrong because statement 2 is also correct. B is wrong because statement 1 is also correct. D is wrong because both statements are correct.
Exam tip: P = primary, push-pull, passes all media; S = secondary, shear, solids only.
Practice Questions
View allWhich one of the following is not a land use category?
- A.Forestland
- B.Pasture land
- C.Marginal land
- D.Barren and wasteland
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India's land-use records follow a nine-fold classification, and 'marginal land' is not one of its classes.
Read the full explanation →Climax mine, the largest producer of molybdenum, is located in
- A.Canada
- B.USA
- C.Australia
- D.South Africa
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The Climax mine is in Colorado, in the Rocky Mountains near Leadville, and it was long the world's largest molybdenum mine.
Read the full explanation →Which one of the following statements about the Coriolis force is not correct ?
- A.It is maximum at the Poles.
- B.It is absent at the Equator.
- C.It deflects the wind to the right direction in the southern hemisphere.
- D.It deflects the wind to the right direction in the northern hemisphere.
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In the southern hemisphere the Coriolis force turns winds to the left, not the right. The Coriolis force is an apparent force caused by the Earth's rotation.
Read the full explanation →Which of the following statements regarding continent of Antarctica is/are correct? 1. It has the highest average elevation as compared to all other continents. 2. Mount Vinson is the highest peak of this continent. Select the correct answer using the code given below.
- A.1 only
- B.2 only
- C.Both 1 and 2
- D.Neither 1 nor 2
Show answer
Antarctica is the highest continent on average, and Mount Vinson is its highest peak. Antarctica's average elevation is about 2,500 metres, far above that of any other continent; Asia, the next highest, averages under 1,000 metres.
Read the full explanation →The ratio of gross cropped area to the net sown area is called
- A.cropping intensity
- B.intensity of crop rotation
- C.crop productivity
- D.cropping diversity
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Cropping intensity is gross cropped area divided by net sown area, usually shown as a percentage, and it tells how many times the same land is cropped in a year.
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