If the wavelengths corresponding to ultraviolet, visible and infrared radiations are given as λUV, λVIS and λIR respectively, then which one of the following gives the correct relationship among these wavelengths?
- A.λUV < λIR < λVIS
- B.λUV > λVIS > λIR
- C.λUV > λIR > λVIS
- D.λUV < λVIS < λIR
Correct answer
Explanation
The correct answer is D, λUV < λVIS < λIR. Ultraviolet rays have the shortest wavelength of the three, visible light comes next and infrared rays have the longest.
The electromagnetic spectrum, in order of increasing wavelength, runs from gamma rays and X-rays to ultraviolet, visible light, infrared, microwaves and radio waves. Visible light spans roughly 400 nm (violet) to 700 nm (red). Ultraviolet lies just beyond violet, below about 400 nm, which is why it is called ultra-violet. Infrared lies just beyond red, above about 700 nm, hence infra-red. Since energy is inversely proportional to wavelength, ultraviolet photons carry more energy than visible ones, which is why UV causes sunburn while infrared is felt as heat.
Option A is wrong because it places infrared below visible light. Option B is wrong because it reverses the whole order. Option C is wrong because it makes ultraviolet the longest and visible the shortest.
Exam tip: wavelength order: gamma < X-ray < UV < visible (violet to red) < IR < microwave < radio.
Practice Questions
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- 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
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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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