A system proposed by the US. Navy for underwater submarine communication, called
ID: 488652 • Letter: A
Question
A system proposed by the US. Navy for underwater submarine communication, called ELF (extremely low frequency), operates with a frequency of 76 Hz. What is the wavelength of radiation in maters? In miles? (1 mile = 1.61 km) What is the energy in joules of the frequency given in question 3? Red and green light have wavelengths of about 650 nm and 490 nm, respectively, which light has the higher frequency red or green? Which light has the higher frequency-red or green? Which light has the higher energy-red or green? Mg emits radiation at 285 nm. Could a spectroscope be used to detect this emission?Explanation / Answer
3) = c/ v = 3X108ms-1/76Hz (Hz = s-1) (c, speed of light = 3X108ms-1 )
= 3X108s-1/76s-1
= 3.95X106 m
= 3.95X103
= 3950km
= 3950/1.61 ( given, 1mile = 1.61 km))
= 2453.4 miles
4) h = 6.63 X 10-34 Js
E= h v = 6.63 X 10-34X 76 s-1 (Hz = s-1)
= 503.9 X 10-34 J
5) According de Broglie equation
1/ v
E 1/
Higher the wavelength, lower is the frequency.
So, Red light ( = 650 nm) is of lower frequency than that of Green light ( = 490 nm);
6) Mg emits radiation at 285 nm. Could a spectroscope be used to detect this emission?
UV spectroscopy can detect radiation in the range of 200nm to 400 nm (approximately). So the radiation emitted by Mg, i.e., 285 nm can be detected by using UV spectroscopy.
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