Compared to audible sound waves, ultrasound waves have
- A.higher speed.
- B.higher frequency.
- C.longer wavelength.
- D.both higher speed and frequency.
Correct answer
Explanation
The correct answer is B, higher frequency. Ultrasound is sound with a frequency above 20,000 hertz, the upper limit of human hearing, so its defining feature is a higher frequency than audible sound. The human ear hears roughly from 20 hertz to 20 kilohertz. Sound below that range is called infrasound and sound above it ultrasound. Bats, dolphins and dogs can produce or hear ultrasound, and doctors use it for sonography, while ships use it in SONAR to find depth and underwater objects. Its short wavelength lets it travel in narrow beams and reflect well from small objects. Option A is wrong because the speed of sound depends on the medium and its temperature, not on frequency, so ultrasound and audible sound travel equally fast in the same medium, about 343 metres per second in air at 20 °C. Option C is wrong because, at the same speed, a higher frequency means a shorter wavelength, not a longer one. Option D is wrong because only the frequency is higher; the speed is the same. Exam tip: infrasound below 20 Hz, audible 20 Hz to 20 kHz, ultrasound above 20 kHz; speed depends on the medium, not on frequency.
Practice Questions
View allThe fact that the planets move around the Sun, not in circles but in ellipses, was first demonstrated by
- A.Galileo
- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
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In 1609 Kepler showed that the planets move around the Sun in elliptical orbits, with the Sun at one focus of the ellipse.
Read the full explanation →Which one of the following statements is correct?
- A.Urea is produced in liver.
- B.Urea is produced in blood.
- C.Urea is produced from digestion of starch.
- D.Urea is produced in lung and kidney.
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Liver cells turn the toxic ammonia released from the breakdown of amino acids into urea through the ornithine cycle, also called the urea cycle.
Read the full explanation →Which one of the following is the correct sequence of passage of light in a compound microscope?
- A.Condenser-Objective lens-Eyepiece-Body tube
- B.Objective lens-Condenser-Body tube-Eyepiece
- C.Condenser-Objective lens-Body tube-Eyepiece
- D.Eyepiece-Objective lens-Body tube-Mirror
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Light passes through the condenser to the specimen, is picked up by the objective lens, travels up the body tube and reaches the eye through the eyepiece.
Read the full explanation →Which one of the following statements regarding haemoglobin is correct?
- A.Haemoglobin present in RBC can carry only oxygen but not carbon dioxide.
- B.Haemoglobin of RBC can carry both oxygen and carbon dioxide.
- C.Haemoglobin of RBC can carry only carbon dioxide.
- D.Haemoglobin is only used for blood clotting and not for carrying gases.
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It binds oxygen at its iron-containing haem groups and carries some carbon dioxide on its protein chains. Each haemoglobin molecule has four polypeptide chains and four haem groups, and each haem iron can hold one oxygen molecule, forming oxyhaemoglobin in the lungs.
Read the full explanation →Which one of the following statements regarding histone proteins is correct?
- A.Histones are proteins that are present in mitochondrial membrane.
- B.Histones are proteins that are present in nucleus in association with DNA.
- C.Histones are proteins associated with lipids in the cytosol.
- D.Histones are proteins associated with carbohydrates in the cytosol.
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They are the proteins around which DNA winds to form chromatin in the nucleus of eukaryotic cells. Histones are small basic proteins, rich in the positively charged amino acids lysine and arginine, which attract the negatively charged phosphate groups of DNA.
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