The speed of the wind is measured by
- A.wind vane
- B.wind rose
- C.barometer
- D.anemometer
Correct answer
Explanation
The correct answer is D, anemometer. An anemometer measures how fast the wind is blowing; its name comes from the Greek word anemos, meaning wind.
The most familiar type is the cup anemometer, which has three or four hemispherical cups on horizontal arms fixed to a vertical shaft; the faster the wind, the faster the cups spin, and the rate of rotation gives the wind speed. Other types use a propeller, a heated wire or sound pulses. Wind speed is reported in kilometres per hour, metres per second or knots, and can also be estimated by eye on the Beaufort scale from 0 (calm) to 12 (hurricane).
A is wrong: a wind vane shows the direction from which the wind blows, not its speed.
B is wrong: a wind rose is a diagram that summarises how often the wind blows from each direction at a place.
C is wrong: a barometer measures atmospheric pressure, which helps forecast weather.
Exam tip: anemometer for wind speed, wind vane for wind direction, barometer for pressure, hygrometer for humidity.
Practice Questions
View allBrilliance of diamond is due to
- A.interference of light
- B.diffraction of light
- C.polarization of light
- D.total internal reflection of light
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Light that enters a cut diamond is reflected again and again inside it before it escapes, which makes the stone sparkle.
Read the full explanation →Which one of the following is NOT an electromagnetic wave ?
- A.Light wave
- B.Radio wave
- C.Sound wave
- D.Micro wave
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Sound is a mechanical wave that needs a medium to travel, while the other three are electromagnetic waves. Sound travels as a longitudinal wave of compressions and rarefactions in air, water or solids, which is why it cannot pass through a vacuum.
Read the full explanation →Which one of the following is NOT true for an electromagnetic wave ?
- A.Electromagnetic wave transports energy and momentum
- B.Electromagnetic wave can be polarized and reflected
- C.Electromagnetic wave is longitudinal
- D.Electromagnetic wave propagation is described by the varying electric and magnetic fields
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Electromagnetic waves are transverse, not longitudinal, so this statement is false. In an electromagnetic wave the electric field and the magnetic field oscillate at right angles to each other and both at right angles to the direction in which the wave travels.
Read the full explanation →Which one of the following frequency ranges is sensitive to human ears ?
- A.0-200 Hz
- B.20-20,000 Hz
- C.200-20,000 Hz only
- D.2,000-20,000 Hz only
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The normal human ear hears sound from about 20 hertz to 20,000 hertz, the audible range. Frequency, measured in hertz, is the number of vibrations per second, and it decides the pitch of a sound: the higher the frequency, the shriller the note.
Read the full explanation →The frequency of ultrasound waves is
- A.less than 20 Hz
- B.between 20 Hz and 2 kHz
- C.between 2 kHz and 20 kHz
- D.greater than 20 kHz
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Ultrasound is sound with a frequency above 20,000 Hz, the upper limit of human hearing. Humans hear sound between about 20 Hz and 20 kHz.
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