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Give below are some famous numbers associated with electromagnetic radiation in different contexts in physics. State the part of the e.m. spectrum to which each belongs: (a) 21cm [wavelength emitted by atomic hydrogen in intersteller space]. (b) 1057MHz [Frequency of radiation arising from two close energy levels in hydrogen , known as of the Lamb shift]. (c) 2.7K[temperature associated with the isotropic filling all space-throught to be a relic of the 'big bang' origin of the universe] (d) 5890Å-5896Å (double lines of sodium). (e) 14.4keV(energy of a particular transition in Fe^(57) nucleus associated with a famous high resolution spectroscopic method Mossabuer spectroscopy)]. |
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Answer» Solution :(a) This wavelength corresponds to RADIO waves (SHORT wavelength or high freqenncy end). (b) This frequency alos corresponds to radio WAVE (short wavelength or high frequency end). (c) Given `T=2.7^@K As lambda_mT=0.29cm^@K` `:. Lambda_m=0.29/T=0.29/2.7~=0.11 cm` This wavelength corresponds to microwave region of the ELECTROMAGNETIC spectrum. (d) This wavelength lies in the visible region (yellow) of the electromagnetic spectrum, (E) Here, Energy `E=14.4 keV=14.4xx10^3xx1.6xx10^-19J` As `e=hv:. v=E/h=(14.4xx10^3xx1.6xx10^-19)/(6.6xx10^-34)~=3xx10^11MHz` This frequency lies in the X-ray region of the electromagnetic spectrum, |
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