Tyndall effect is a phenomenon of
- A.scattering of light by the colloidal particles.
- B.refraction of light by the colloidal particles.
- C.dispersion of light by dust particles.
- D.refraction of light by dust particles.
Correct answer
Explanation
The correct answer is A, scattering of light by the colloidal particles. Particles in a colloid are large enough to scatter a beam of light, which makes the path of the beam visible.
The effect is named after the Irish physicist John Tyndall. Colloidal particles are roughly 1 to 1,000 nanometres across, bigger than the molecules of a true solution but too small to settle out. When light passes through a colloid such as milk diluted in water, starch solution or fog, these particles scatter it sideways and the beam shows up as a bright cone. A true solution such as salt or sugar in water does not show the effect. Everyday examples are sunlight streaming through a gap in a dense forest canopy, or a beam from a projector in a dusty, smoky hall.
B is wrong because refraction is the bending of light as it passes from one medium to another, not its spreading by particles. C is wrong because dispersion is the splitting of white light into colours, as in a prism. D is wrong for the same reason as B.
Exam tip: Tyndall effect separates a colloid from a true solution; the scattered beam path is the clue.
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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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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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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