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

Chapter : 11

What are Dual Nature Of Radiation And Matter ?

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=hvΦ=(hc/λ0) Φ = Work function
    h = Planck’s constant
    Vo = Threshold frequency
    λo = 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 = kmax + Φ0
    or
    kmax = h – Φ0
    or
    ev0 = hv – hv0    		 h = Planck’s constant
    v = Frequency of the incident photon
    kmax = 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.