Modern Physics One Shot Part‑1 Photoelectric Effect & Dual Nature Class 12 Physics JEE Main скачать в хорошем качестве

Modern Physics One Shot Part‑1 Photoelectric Effect & Dual Nature Class 12 Physics JEE Main

Modern Physics One Shot (Part‑1): Photoelectric Effect & Dual Nature – Class 12 Physics & JEE Main In this one‑shot revision lecture, we cover the entire Photoelectric Effect + Dual Nature of Radiation and Matter in a fast but concept‑first way – perfect for CBSE Class 12 boards and JEE Main. We start from the photoelectric experiment, go through the failure of classical wave theory, then derive and apply Einstein’s photoelectric equation, and finally move to the de Broglie hypothesis and numericals. 🔍 Topics Covered 1. Photoelectric Effect – Experiment & Observations Photoelectric effect setup: cathode, anode, applied potential Definition of photoelectrons and photoelectric current Key experimental facts: Threshold frequency (f_0) Instantaneous emission (no time lag) Kinetic energy depends on frequency, not intensity Photoelectric current depends on intensity 2. Failure of Classical Wave Theory Why wave theory predicts: Time lag at low intensity KE ∝ intensity, not frequency No sharp threshold How experiments contradict this 3. Einstein’s Photon Theory & Photoelectric Equation Photon picture of light Photon energy: (E = hf = hc/\lambda) Work function (\phi) and threshold frequency (f_0) Einstein’s equation: [ hf = \phi + K_\text{max},\quad K_\text{max} = hf - \phi ] Threshold condition: (\phi = hf_0), so (K_\text{max} = h(f - f_0)) 4. Stopping Potential & Important Graphs Retarding potential and stopping (cut‑off) potential (V_0) [ eV_0 = K_\text{max} ] Relation: [ V_0 = \frac{h}{e} f - \frac{\phi}{e} ] Graphs: (K_\text{max}) vs frequency (f) (V_0) vs frequency (f) (slope = (h/e)) Photoelectric current vs voltage for different intensities 5. Numericals on Photoelectric Effect Threshold frequency → work function in eV Photon energy using (E(\text{eV}) = 1240/\lambda(\text{nm})) Maximum kinetic energy and stopping potential (V_0) ⚡ Dual Nature: Radiation & Matter 6. Dual Nature of Radiation (Photons) Wave vs particle picture of light Photon energy: (E = hf) Photon momentum: (p = E/c = h/\lambda) Intensity as number of photons per unit area per second Radiation pressure (concept only) 7. Evidence for Matter Waves Electron diffraction from a crystal (diagram + explanation) Why electron wavelength (\lambda_e) comparable to atomic spacing de Broglie relation: (\lambda = h/p) 8. de Broglie Wavelength & Electrons Accelerated Through V de Broglie wavelength: [ \lambda = \frac{h}{p} = \frac{h}{mv} ] Electron accelerated from rest through potential difference (V): [ eV = \frac{1}{2}mv^2,\quad \lambda = \frac{h}{\sqrt{2meV}} \propto \frac{1}{\sqrt{V}} ] Why increasing (V) decreases (\lambda), and its use in electron microscopes 9. Numericals on de Broglie Wavelength Electron accelerated through 150 V → (\lambda) ≈ 0.1 nm Proton with given speed → nuclear‑scale de Broglie wavelength 📌 Formula Recap (Boards + JEE Main) Photoelectric Effect: (E = hf = hc/\lambda) (\phi = hf_0) (K_\text{max} = hf - \phi) (eV_0 = K_\text{max}) (V_0 = (h/e) f - \phi/e) Dual Nature: Photons: (E = hf,\ p = h/\lambda,\ E = pc) Matter waves: (\lambda = h/p = h/(mv)) Electron through V: (\lambda = h/\sqrt{2meV} \propto 1/\sqrt{V}) ✅ Who Should Watch? Class 12 CBSE Physics students revising Modern Physics JEE Main aspirants needing a quick but conceptual revision of: Photoelectric effect graphs and numericals Threshold frequency & work function de Broglie wavelength & electrons accelerated through V This is Modern Physics One‑Shot (Part‑1). Watch Part‑2 next for Bohr model, hydrogen spectrum, atoms & nuclei basics.