Question

28.
The wavelength 21 cm emitted by atomic hydro-
gen in interstellar space belongs to
(1) infrared waves (2) radio waves
(3)
Y -rays
(4) microwaves​

Answer 1

Answer:

Radio Waves Most of the hydrogen gas in the interstellar medium is in cold atomic form or molecular form. Hendrik van de Hulst predicted that the cold atomic hydrogen (H) gas should emit a particular wavelength of radio energy from a slight energy change in the hydrogen atoms. The wavelength is 21.1 cm (frequency = 1420.4 MHz).

So, this radiation belongs to radio waves.

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