# The terminology of different parts of the electromagnetic spectrum is given in the text. Use the formula E = hv (for energy of a quantum of radiation: photon) and obtain the photon energy in units - Physics

Numerical

The terminology of different parts of the electromagnetic spectrum is given in the text. Use the formula E = hv (for energy of a quantum of radiation: photon) and obtain the photon energy in units of eV for different parts of the electromagnetic spectrum. In what way are the different scales of photon energies that you obtain related to the sources of electromagnetic radiation?

#### Solution

Energy of a photon is given as:

"E" = "hv" = ("hc")/lambda

Where,

h = Planck’s constant = 6.6 × 10−34 Js

c = Speed of light = 3 × 108 m/s

∴ E = (6.6 xx 10^-34 xx 3 xx 10^8)/lambda

= (19.8 xx 10^-26)/lambda J

= (19.8 xx 10^-26)/(lambda xx 1.6xx10^-19) J

= (12.375 xx 10^-7)/lambda "eV"

The given table lists the photon energies for different parts of an electromagnetic spectrum for different λ.

 λ (m) 103 1 10−3 10−6 10−8 10−10 10−12 E (eV) 12.375 × 10−10 12.375 × 10−7 12.375 × 10−4 12.375 × 10−1 12.375 × 101 12.375 × 103 12.375 × 105

The photon energies for the different parts of the spectrum of a source indicate the spacing of the relevant energy levels of the source.

Concept: Electromagnetic Spectrum
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#### APPEARS IN

NCERT Physics Part 1 and 2 Class 12
Chapter 8 Electromagnetic Waves
Exercise | Q 8.9 | Page 286
NCERT Class 12 Physics Textbook
Chapter 8 Electromagnetic Waves
Exercise | Q 9 | Page 286

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