Dual Nature Of Radiation And Matter Class 12 Notes Physics Chapter 11 - CBSE

Chapter : 11

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Topic Name	Formula	Symbol Representation	Important Points
Photon Theory of Light	E = hv=(hc/λ)joule or E =(hc/λ) =(1240/λ)eVnm	E = Energy of photon, h = Planck’s constant, v = Frequency of photon c = Speed of light λ = Wavelength of photon e = Charge of electron	Packets of energy which are emitted by source of radiation they travelled in straight line. The rest mass of photon is zero Frequency of photon does not change when it passes through different medium but its wavelength change. Momentum of photon is (hv/c) or (h/λ)
Intensity of Light	I =(E/At)=(P/A)	I = Intensity of light E = Incident energy t = Time taken A = Area of surface P = Power of source	Energy of light passing through per unit area of a surface per unit time is known as intensity of light. When radiation of suitable wavelength or frequency is incident on a metal, electrons are ejected. This effect is known as photoelectric effect. Photoelectric effect varifies quantum nature of light. Photoelectric effect is based on the law of conservation of energy. Alkali metals, like lithium, sodium, potassium, caesium etc. show photo electric effect with visible light.
Work Function	Φ=hv_Φ=(hc/λ₀)	Φ = Work function h = Planck’s constant V_o = Threshold frequency λ_o = Threshold wavelength	The minimum energy of the incident photon below which these will be no ejection of photoelectrons from a metal surface, is known as work function or threshold energy for that metal.

Topic Name	Formula	Symbol Representation	Important Points
Einstein’s equation of photoelectric effect	hv = k_max + Φ₀ or k_max = h – Φ₀ or ev₀ = hv – hv₀	h = Planck’s constant v = Frequency of the incident photon k_max = Maximum kinetic energy of ejected electrons Φ₀ = Work function of the metal U₀ = Stopping potential V₀ = Threshold frequency e = Charge on electron	• According to Einstein, photon energy is utilized for two purposes, partly for getting the electrons free from the atom and away from the metal surface known as the work function of the metal (Φ₀) and the remaining photon energy is used up in providing the electrons kinetic energy of (1/2)mv²
de-Broglie Hypothesis of Matter Waves	λ=(h/p)=(h/mv)=(h/√2mE)	λ = de-Broglie wavelength or wavelength associated with particle p = momentum of the particle m = mass of the moving particle v = velocity of the moving particle E = kinetic energy of the moving particle	• According to de-Broglie hypothesis, a moving particle sometimes acts as a wave and sometimes as a particle. The wave associated with waving particle is called matter waves or de-Broglie waves.