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Question

Given below are some famous numbers associated with electromagnetic radiations in different contexts in physics. State the part of the electromagnetic spectrum to which each belongs.
(a) 21 cm (wavelength emitted by atomic hydrogen in interstellar space).

(b) 1057 MHz (frequency of radiation arising from two close energy levels in hydrogen; known as Lamb shift).

(c) 2.7 K [temperature associated with the isotropic radiation filling all space thought to be a relic of the big-bang origin of the universe].

(d) 5890˚A5896˚A [double lines of sodium]

(e) 14.4 ke V [energy of a particular transition in 57Fe nucleus associated with a famous high resolution spectroscopic method (M¨ossbauer spectroscopy)].

Solution
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(a)
Radio waves have wavelengths of 1mm to 100km. Hence, 21cm lies at short wavelength end of radio waves.

(b)

Radio waves belong to the shortest wavelength in the electromagnetic spectrum.

(c)

λm=0.29/T=0.11cm

This wavelength corresponds to the microwaves.

(d)

Lines from 400nm to 700nm lies in visible range. The range of 589nm lies in Yellow part of visible spectrum.

(e)

E=hν

ν=3.4×1018Hz

This corresponds to the X-rays.

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Similar Questions
Q1
Given below are some famous numbers associated with electromagnetic radiations in different contexts in physics. State the part of the electromagnetic spectrum to which each belongs.
(a) 21 cm (wavelength emitted by atomic hydrogen in interstellar space).

(b) 1057 MHz (frequency of radiation arising from two close energy levels in hydrogen; known as Lamb shift).

(c) 2.7 K [temperature associated with the isotropic radiation filling all space thought to be a relic of the big-bang origin of the universe].

(d) 5890˚A5896˚A [double lines of sodium]

(e) 14.4 ke V [energy of a particular transition in 57Fe nucleus associated with a famous high resolution spectroscopic method (M¨ossbauer spectroscopy)].
View Solution
Q2

Given below are some famous numbers associated with electromagnetic radiations in different contexts in physics. State the part of the electromagnetic spectrum to which each belongs.

(a) 21 cm (wavelength emitted by atomic hydrogen in interstellar space).

(b) 1057 MHz (frequency of radiation arising from two close energy levels in hydrogen; known as Lamb shift).

(c) 2.7 K [temperature associated with the isotropic radiation filling all space-thought to be a relic of the ‘big-bang’ origin of the universe].

(d) 5890 Å - 5896 Å [double lines of sodium]

(e) 14.4 keV [energy of a particular transition in 57Fe nucleus associated with a famous high resolution spectroscopic method

(Mössbauer spectroscopy)].

View Solution
Q3
Match the List -I (Phenomenon associated with electromagnetic radiation) with List - II (Part of electromagnetic spectrum) and select the correct code from the choices given below the

List - I

List - II
I
Doublet of sodium
A
Visible radiation
II
Wavelength corresponding to temperature associated with the isotropic radiation filling all space
B
Microwave
III
Wavelength emitted by atomic hydrogen in interstellar space
C
Short radiowave
IV
Wavelength of radiation arising from two close energy levels in hydrogen
D
X-rays

View Solution
Q4
The frequency of radiations arising from two close energy levels in hydrogen, known as lamb shift is 1057 MHz. This frequency falls in which range of electromagnetic waves?
View Solution
Q5
Calculate the wavelength of the radiations emitted when an electron in a hydrogen atom undergoes a transition from 4th energy level to the 2nd energy level. In which part of the electromagnetic spectrum does this line lie?
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