Explain the wave-particle duality of light. (b) A... | WAEC SSCE - Physics - 2021 (Essay)

Question 1 Report

Explain the wave-particle duality of light. (b) A particle of wavelength 4.2x 10\(^{-11}\)m travels (a) With a momentum of 1.6 x 10\(^{-23}\) kg m/s,

Determine the value of the Planck's constant, h.

Answer

(a) Wave-particle duality of light. Light shows a dual nature. In some experiments it behaves as a wave (it undergoes interference, diffraction and polarisation, as in Young's double-slit experiment), while in other experiments it behaves as a stream of particles called photons, each carrying energy \(E=hf\) (as in the photoelectric effect and the Compton effect). Light is therefore neither purely a wave nor purely a particle; it exhibits whichever behaviour the experiment probes. The two aspects are linked by the de Broglie relation \(\lambda = h/p\).

(b) Finding Planck's constant. The de Broglie relation connects wavelength and momentum:

\[ \lambda = \frac{h}{p} \quad\Rightarrow\quad h = \lambda p \]

With \(\lambda = 4.2\times10^{-11}\ \text{m}\) and \(p = 1.6\times10^{-23}\ \text{kg m/s}\):

\[ h = (4.2\times10^{-11})(1.6\times10^{-23}) \] \[ h = 6.72\times10^{-34}\ \text{J s} \]

Planck's constant is about \(6.72\times10^{-34}\ \text{J s}\), in good agreement with the accepted value \(6.63\times10^{-34}\ \text{J s}\).

Read lesson note on Wave-particle Paradox (WAEC)

Read lesson note on Structure Of Matter And Kinetic Theory (JAMB)

Answer Details

(b) Finding Planck's constant. The de Broglie relation connects wavelength and momentum:

\[ \lambda = \frac{h}{p} \quad\Rightarrow\quad h = \lambda p \]

With \(\lambda = 4.2\times10^{-11}\ \text{m}\) and \(p = 1.6\times10^{-23}\ \text{kg m/s}\):

\[ h = (4.2\times10^{-11})(1.6\times10^{-23}) \] \[ h = 6.72\times10^{-34}\ \text{J s} \]

Planck's constant is about \(6.72\times10^{-34}\ \text{J s}\), in good agreement with the accepted value \(6.63\times10^{-34}\ \text{J s}\).

Read lesson note on Wave-particle Paradox (WAEC)

Read lesson note on Structure Of Matter And Kinetic Theory (JAMB)

Wave-particle Paradox

Structure Of Matter And Kinetic Theory

View Answer

Explain the wave-particle duality of light. (b) A particle of wavelength 4.2x 10\(^{-11}\)m travels (a) With a momentum of 1.6 x 10\(^{-23}\) kg m/s, Determ...

Download The App On Google Playstore

Explain the wave-particle duality of light. (b) A particle of wavelength 4.2x 10\(^{-11}\)m travels (a) With a momentum of 1.6 x 10\(^{-23}\) kg m/s, Determ...

Related Questions

Download The App On Google Playstore