Advertisements
Advertisements
Question
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?
Advertisements
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
λ = Wavelength of radiation
∴ 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.
RELATED QUESTIONS
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)].
Name the electromagnetic radiations used for (a) water purification, and (b) eye surgery.
What do you understand by the statement, "Electromagnetic waves transport momentum"?
State the approximate range of wavelength associated with visible light.
Name the waves used for taking photographs in dark.
Name the waves of wavelength nearly 0.1 nm.
Two waves A and B have wavelength 0.01 Å and 9000 Å respectively.
- Name the two waves.
- Compare the speeds of these waves when they travel in vacuum.
The wavelength of X-rays is 0.01 Å. Calculate its frequency. State the assumption made, if any.
Which part of electromagnetic spectrum is used in radar systems?
Can X-rays be polarised?
Find the cutoff wavelength for the continuous X-rays coming from an X-ray tube operating at 30 kV.
(Use Planck constant h = 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
Name the scientist who discovered Visible light
Identify the part of the electromagnetic spectrum used in (i) radar and (ii) eye surgery. Write their frequency range.
Name the radiation of the electromagnetic spectrum which is used for the following:
For taking photographs of the sky during the night and foggy conditions . Give the frequency range
Name any two electromagnetic waves which have a frequency higher than that of violet light. State one use of each.
Following QN ∴ 14, the radiation force on the roof will be
If λv, λx and λm Am represents the wavelength of visible light, x-ray and microwaves respectively, then ______.
One requires 11eV of energy to dissociate a carbon monoxide molecule into carbon and oxygen atoms. The minimum frequency of the appropriate electromagnetic radiation to achieve the dissociation lies in ______.
What happens when an electron collides with a positron?
How does the frequency of infrared radiation compare with that of microwaves?
