Dual Nature Of Radiation And Matter

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Common Misconceptions

4 min read

- What you are getting from a statement might not be necessarily true. Let's burst some of the common misconceptions

The objects exhibit dual nature simultaneously.
The answer is a big NO. Radiation appears to possess dual character. It sometimes behaves as waves and other times as particles. For example, radiation is considered as a wave in propagation experiments like interference, diffraction and polarisation. These experiments firmly establish the wave nature of radiation.
On the other hand , the phenomena like photoelectric effect, Compton effect, Ramon effect etc shows that the radiation behaves as particles - photons. Thus radiation has a dual characteristic. However, radiation does not exhibit its its wave and particle aspect simultaneously. It is found to behave as a wave in transmission and as a particle, when it interacts with matter.

Electron can reside in a nucleus since an electron is emitted in beta decay.
For the electron to be confined in a nucleus of radius

r \sim 1 0^{- 15}

,the uncertainty in its position would be

Δ r = 1 0^{- 15}

. Since

Δ r . Δ p = \frac{h}{2 π}

we can calculate

Δ v = 5.7 \times 1 0^{10} m/s

, which is greater than the speed of light. No speed can not cross the speed of light. Therefore we can conclude that electrons can not reside in a nucleus. The electron in beta decay is actually a result of conversion of a neutron into a proton and an electron, i.e.

n \to p + e + anti-nutrino

de Broglie's wave is not associated with a macroscopic object.
The general rule is : whenever the De Broglie wavelength of an object is in the range of , or exceeds, it's size , the wave nature of the object is detectable and hence cannot be neglected. But if the De Broglie wavelength is much too small compared to its size, the wave behavior of this object is undetectable.
We may conclude that, whereas the wavelengths associated with the microscopic systems are finite and display easily detectable wave-like patterns, the wavelengths associated with the macroscopic systems are infinitesimally small and display no discernible wave-like behavior.

Bohr orbits are sharp energy levels.
According to Bohr's concept, each electron revolves in quantized orbits having a sharply defined energy , with no uncertainity whatsover. So,

Δ E = 0

Δ t = \infty

. That is, all energy state of the atom have infinite life-time, implying impossibility of radiation due transition between orbits. In fact,

Δ t \sim 1 0^{- 8} sec

. The concept of Bohr's orbit thus violates the uncertainity principle. Conversely the finite life-time

Δ t

endows

Δ E

a value

\sim \frac{h}{2 π} . Δ t

., that is a finite width to energy levels. It implies that the excited energy levels have a finite energy spread. So, during transition from an excited energy state to the ground state, the radiation is not truly monochromatic. This means spectral lines can never be infinitely sharp but must have a natural finite width (natural broadening).