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CBSE NOTES CLASS 12 PHYSICS

CHAPTER 11 DUAL NATURE OF RADIATION AND MATTER

Causes of cathode ray emmission

Properties of cathode rays

Photon

Photoelectric effect

Work function

Threshold frequency

Threshold wavelength

Laws of photoelectric effect

Effect of intensity of incident light on photoelectric current

Effect of potential on photoelectric current

Effect of frequency on photoelectric current

Photoelectric emission is an instantaneous process

Failure of wave theory in explaining photoelectric effect

Einstein’s photoelectric equation: energy quantum of radiation

Particle nature of light

Wave nature of matter

Heisenberg’s uncertainty principle

CBSE NOTES CLASS 12 PHYSICS

CHAPTER 11 DUAL NATURE OF RADIATION AND MATTER

Photon

Photons are the packets of energy emitted by a source of radiation. The energy of each photon is,

E = hν,

where h is Planck’s constant and ν is frequency of radiation.

The rest mass of a photon is zero.

The momentum of a photon

p =hνc=hλ

Dynamic or kinetic mass of photon,

 m =hνc2=hcλ 

where c is speed of light in vacuum and λ is wavelength of radiation.

Photons are electrically neutral.

A body can radiate or absorb energy in whole number multiples of a quantum, that is hν, 2hν, 3hν …, nhν, where n is positive integer.

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