Which one of the following statements is not correct?
- A.The cathode rays originate from cathode and proceed towards the anode in a cathode-ray discharge tube.
- B.The television picture tubes are nothing but cathode-ray tubes.
- C.The cathode rays themselves are not visible.
- D.The characteristics of cathode rays depend upon the nature of the gas present in the cathode-ray tube.
Correct answer
Explanation
The correct answer is D, The characteristics of cathode rays depend upon the nature of the gas present in the cathode-ray tube.. Cathode rays behave the same whatever gas is in the tube, so the statement that they depend on the gas is not correct.
Cathode rays are streams of electrons that leave the cathode and travel in straight lines towards the anode when a high voltage is applied across a gas at very low pressure. J. J. Thomson showed in 1897 that their charge-to-mass ratio is the same for every gas and every cathode metal, which proved that electrons are a common part of all atoms. The rays cannot be seen directly; they are detected when they strike a coating such as zinc sulphide and make it glow.
A is wrong as a choice because the rays do start at the cathode and move to the anode. B is wrong as a choice because old television picture tubes were indeed cathode-ray tubes. C is wrong as a choice because the rays are invisible and show up only through fluorescence.
Exam tip: Cathode rays: electrons, cathode to anode, straight lines, invisible, e/m independent of gas (J. J. Thomson, 1897).
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
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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