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Wavelengths of Electromagnetic Radiations
Wavelengths of Electromagnetic Radiations:
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Electromagnetic radiations
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Wave length (Å)
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Radio waves
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3 x1014 to 3 x107
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Micro waves
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3 x109 to 3 x106
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Infrared (IR)
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6 x106 to 7600
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1.1.1 Visible
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7600 to 3800
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Ultra violet (UV)
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3800 to 150
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X–rays
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150 to 0.1
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Gamma rays
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0.1 to 0.01
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Cosmic rays
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0.01 to zero
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Illustration:
Find out the longest wavelength of absorption line for hydrogen gas containing atoms in ground state.
Solution:
1 / λ = RZ2 [ 1/ n12 - 1/ n22 ]
For longest wavelength ¦E should be smallest, i.e. transition occurs from
n = 1 to n = 2
n = 7 ————————————
n = 6 ————————————
n = 5 ————————————
n = 4 ————————————
n = 3 ————————————
i.e. 1 / λ = 109673 cm–1 ´ 12 [ 1 /12 - 1 / 22 ]
... 1 / λ = 109673 x 3 / 4 cm–1
... λ = 4 / 3 x 109673cm-1= 1.2157 x 10–5 cm = 121.6 nm