Rapid electron acceleration and deceleration in a conducting wire can generate _______ with frequencies ranging from ______.
long radio waves, a few Hz to a few MHz
Radio Waves from Electron Motion
When electrons in a conducting wire undergo rapid acceleration and deceleration, they act as oscillating electric charges. According to the principles of electromagnetism, any accelerating or decelerating charge radiates energy in the form of electromagnetic waves. The type of electromagnetic wave produced depends on the frequency of this oscillation or the energy involved in the acceleration.
Electron Oscillation and Radio Wave Generation
In a conducting wire, if an alternating current (AC) is applied, the free electrons within the wire are forced to move back and forth, constantly accelerating and decelerating. This oscillation of charges creates changing electric and magnetic fields that propagate outwards as electromagnetic waves. These waves are commonly known as radio waves.
- Generation Mechanism: The back-and-forth movement (oscillation) of electrons in an antenna or a conducting wire due to an alternating current causes them to accelerate and decelerate. This motion directly generates electromagnetic waves.
- Nature of Waves: The waves generated by this process, particularly at lower frequencies, are categorized as radio waves.
Frequency Range of Long Radio Waves
The electromagnetic spectrum covers a vast range of frequencies and wavelengths. Radio waves occupy the lowest frequency end of this spectrum.
- Radio Wave Frequencies: Radio waves have frequencies typically ranging from a few hertz (Hz) up to several gigahertz (GHz).
- Long Radio Waves: The term "long radio waves" specifically refers to the lower frequency portion of the radio spectrum. These waves can have frequencies from a few hertz (Hz) up to a few megahertz (MHz). For example, very low frequency (VLF) radio waves can range from $3$ kHz to $30$ kHz, and medium wave (MW) radio can go up to around $3$ MHz. This range corresponds perfectly with the option of "a few Hz to a few MHz".
Comparing with Other Electromagnetic Waves
Let's consider why the other options are not appropriate for waves generated by rapid electron acceleration and deceleration in a typical conducting wire:
| Wave Type | Typical Frequency Range | Generation Method (usually) | Relevance to Question |
|---|---|---|---|
| Microwaves | $10^{9}$ Hz to $10^{12}$ Hz (or $1$ GHz to $1$ THz) | Specialized electronic devices (e.g., magnetrons, klystrons, Gunn diodes) | Generated by electron motion, but at much higher frequencies usually not from simple wire oscillations at the stated range. |
| Infrared rays | $10^{12}$ Hz to $10^{14}$ Hz (or $1$ THz to $100$ THz) | Thermal motion and vibrations of atoms and molecules | Not primarily generated by electron acceleration/deceleration in a wire. |
| X-rays | $10^{16}$ Hz to $10^{20}$ Hz | Rapid deceleration of high-energy electrons (Bremsstrahlung) or electron transitions in inner atomic shells. | Requires much higher energies and different mechanisms than simple wire oscillations. |
Therefore, rapid electron acceleration and deceleration in a conducting wire are the primary method for generating radio waves, especially the lower frequency "long radio waves" in the range of a few Hz to a few MHz.
Important Questions from Dual Nature: Photon and Matter Waves
The wavelength of the matter waves associated with a fast moving sub-atomic particle depends upon
(i) charge
(ii) mass
(iii) velocity
(iv) spin state and
(v) momentum
The correct factors are
In a photoelectric experiment, both sodium (work function = 2.3 eV) and tungsten (work function = 4.5 eV) metals are illuminated by an ultraviolet light of same wavelength. If the stopping potential for tungsten is measured to be 1.8 V, then the value of the stopping potential for sodium will be
Schrodinger wave equation can be written as:
Energy of a photon of wavelength 5890A° emitted by sodium vapour lamp is
The experimental evidence that the electron exhibits wave-like characteristics was first provided by:
