Which of the following statements is NOT correct regarding the travel of sound waves?
- A.Sound waves can travel through water
- B.Sound waves can travel through air
- C.Sound waves can travel through steel
- D.Sound waves can travel through vacuum
Correct answer
Explanation
The correct answer is D, sound waves can travel through vacuum. Sound is a mechanical wave that needs a medium, so it cannot pass through empty space.
Sound travels as a series of compressions and rarefactions passed from particle to particle of a medium. In a vacuum there are no particles to vibrate, so sound cannot move. The classic bell jar experiment shows this: as air is pumped out of a jar holding a ringing electric bell, the sound grows fainter until it is barely heard. This is also why astronauts in space talk by radio, since electromagnetic waves need no medium. Sound moves fastest in solids, slower in liquids and slowest in gases.
A is wrong as an answer because sound does travel through water, at about 1,500 m/s.
B is wrong as an answer because sound travels through air, at about 343 m/s at 20°C.
C is wrong as an answer because sound travels through steel, at roughly 5,000 m/s or more.
Exam tip: speed of sound is greatest in solids, then liquids, then gases, and zero in a vacuum.
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
Show answer
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
Show answer
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.
Show answer
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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