RAS question
A seismograph is used to:
Correct answer: (C) Detect and record earthquake waves.
A seismograph is used to detect and record seismic waves and the ground motion caused by earthquakes, explosions, or other Earth-shaking events.
Explanation
A seismograph is the instrument used for earthquake recording because its job is to make a record of seismic waves caused by an earthquake, explosion, or similar Earth-shaking phenomenon. Britannica also notes the useful distinction between a seismometer and a seismograph: both may detect and measure seismic waves, but a seismograph has the capacity to record them. That recorded output is called a seismogram. This is why option C is the precise answer, not merely a loose association with earthquakes. The instrument converts ground motion into a record that can be studied, and earthquake scales such as the Richter and Moment Magnitude scales use seismograph readings to express earthquake intensity.
Why the other options are wrong
- (A) Humidity is not a seismic-wave measurement; it is measured by a hygrometer, not by a seismograph.
- (B) Atmospheric pressure is measured by a barometer, whereas a seismograph records ground motion from seismic waves.
- (D) Wind speed is measured by an anemometer, while a seismograph is concerned with earthquake-related ground motion.
Concept
This tests basic scientific instruments under Science and Technology, especially matching a device with the physical quantity or phenomenon it records. Such questions recur in RAS because disaster awareness and elementary geoscience both require knowing how earthquakes are detected and recorded.