NEET Physics Dual Nature of Radiation And Matter Notes
Dual Nature of Radiation and Matter
The energy gained by an electron when it is accelerated between a potential difference of 1 volt is called 1eV.
The minimum energy required by an electron to escape from the metal surface is called work function \(\left(\phi_0\right)\)
Caesium (Cs) has the least work function (2.14 eV)
Read And Learn More: NEET Physics Notes
Platinum (Pt) has the highest work function (5.65 eV)
The phenomenon of emission of free electrons from a metal surface on illumination of electromagnetic radiation of suitable frequency is called the Photoelectric Effect.
Maximum kinetic energy of emitted photoelectrons is given by,
\(K_{\max }=e V_0\)where V0 is stopping potential.
Experimental Observations of Photoelectric Effect
Dual Nature of Radiation and Matter NEET Important Questions
1. Above threshold frequency, the photocurrent is directly proportional to intensity of incident light.
2. Saturation current is proportional to intensity of incident radiation but stopping potential is independent of intensity.
Step-by-Step Solutions for Dual Nature NEET Problems
3. There exists a certain minimum frequency below which photoemission is absent is called threshold frequency.
Photoelectric Effect Questions for NEET with Solutions
4. The photoelectric effect is an instantaneous process.
Note: Wave theory of light failed to explain experimental observations of the photoelectric effect.
Einstein’s Explanation for Photoelectric Effect
According to Einstein when a photon of energy falls on a metal surface, the maximum kinetic energy of emitted photoelectrons is given by,
\(K_{\max }=h v-\phi_0 \rightarrow(1)\)Where, is the work function of the metal?
Equation (1) is in the form of y = mx + c
i.e., the graph of \(K_{\max }\)versus will be a straight line with slope h.
\(\begin{aligned}(1) \Rightarrow e V_0 & =h v-\phi_0 \quad\left(∵ K_{\max }=e V_0\right) \\
V_0 & =\left(\frac{h}{e}\right) v-\frac{\phi_0}{e} \rightarrow(2)
\end{aligned}\)
Equation (2) is also in the form of y = mx + c
i.e., the graph V0 of verses is a straight line with slope \(\frac{h}{e}\)
De Broglie Wavelength Formula and Questions for NEET
Important properties of photon
- Momentum of the photon is \(\frac{E}{c}=\frac{h v}{c}\)
- The rest mass of a photon is zero.
- Photons are electrically neutral; they are not deflected by electric or magnetic fields.
Matter waves
Waves associated with moving matter are called matter waves.
According to Louis de Broglie wavelength of matter waves is given by,
\(\lambda=\frac{h}{P}=\frac{h}{m v}\)Consider a particle of mass m and charge q accelerated from rest through a potential V. Then The kinetic energy of the charged particle is given by,
K = qV
\(\text { w.k.t., } \lambda=\frac{h}{P}=\frac{h}{\sqrt{2 m K}}\) \(\Rightarrow \lambda=\frac{h}{\sqrt{2 m q V}}\)For an electron,
\(\lambda=\frac{h}{\sqrt{2 m e V}}=\frac{1.227}{\sqrt{V}} \mathrm{~nm}\)NEET Physics Chapter Wise Weightage Dual Nature of Radiation
Note: Davisson and Germer’s experiment proved the wave nature of electrons.
According to Heisenberg’s uncertainty principle, it is impossible to measure two canonically conjugate physical quantities like the position and momentum of a microscopic entity simultaneously and accurately.
Or in simple form,
It is impossible to measure the position and momentum of a microscopic particle accurately and simultaneously.