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प्रश्न
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?
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उत्तर
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.
संबंधित प्रश्न
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)].
Give a reason for the following:
It is necessary to use satellites for long-distance TV transmission. Why?
Name the phenomenon which shows the quantum nature of electromagnetic radiation.
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(a) Which colour has the greater speed in vacuum?
(b) Which colour has the greater speed in glass?
Arrange the following radiations in the order of their increasing wavelength:
X-rays, infrared rays, ratio waves, gamma ray and microwaves.
State the approximate range of wavelength associated with infrared rays.
Give one use of gamma rays.
Is it possible that in a Coolidge tube characteristic Lα X-rays are emitted but not Kα X-rays?
The electric current in an X-ray tube (from the target to the filament) operating at 40 kV is 10 mA. Assume that on an average, 1% of the total kinetic energy of the electron hitting hte target are converted into X-rays.
(a) What is the total power emitted as X-rays and (b) how much heat is produced in the target every second?
Name the radiation of the electromagnetic spectrum which is used for the following:
To photograph internal parts of the human body and Give the frequency range
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Answer briefly.
Why light waves travel in a vacuum whereas sound waves cannot?
Answer briefly.
Give two uses of radio waves.
The electric field intensity produced by the radiations coming from 100 W bulb at a 3 m distance is E. The electric field intensity produced by the radiations coming from 50 W bulb at the same distance is ______.
What is the wavelength range of electromagnetic radiation used in radio broadcast?
In an atom X, electrons absorb the energy from an external source. This energy “excites” the electrons from a lower-energy level to a higher-energy level around the nucleus of the atom. When electrons return to the ground state, they emit photons.
The figure below is the energy level diagram of atom X with three energy levels, E1 = 0.00eV, E2 = 1.78eV and E3 = 2.95eV. The ground state is considered 0 eV for reference. The transition of electrons takes place between levels E1 and E2.
- What wavelength of radiation is needed to excite the atom to energy level E2 from E1?
- Suppose the external source has a power of 100 W. What would be the rate of photon emission?
What do electromagnetic waves require for propagation?
At what speed do all electromagnetic waves travel in a vacuum?
