Lecture physics a2 quantum nature of light (quantum optics) phd pham tan thi

Quantum Nature of Light Quantum Optics Ho Chi Minh University of Technology Courtesy of N... Light behave like a wave or a particleThis is called the duality of the behavior of light...

Quantum Nature of Light

(Quantum Optics)

Ho Chi Minh University of Technology

Courtesy of N Brunner and J Simmonds

Light behave like a wave or a particle

(This is called the duality of the behavior of light)

Wave Characteristics

Electrically Charged Particles and Electromagnetic Waves

Electrons have (-) charge

Protons have (+) charge

Both have electric fields

+- ++ and

• The changing position of a charged particle creates “waves” called

electromagnetic waves

• The electromagnetic waves travel

through empty space eventually

interacting with a distant charged

• Visible light is an electromagnetic wave

(Effect on electric charges)

Moving electric charges also produce magnetic fields

Example: electric current passing

Another interesting example: the

Earth’ magnetic field is produced by the spinning of charges in the liquid Conversely, magnetic field force charged particles to move…

Accelerated Charges (electrons, protons) Produce

(Ripples in the Electromagnetic Field)

An electromagnetic wave is

composed of two oscillating fields,

and electric field and a magnetic

field perpendicular to each other

Antenna receives electromagnetic signal from TV station

Wavelength of Electromagnetism means COLOR

The Temperature Scale

(Conversion from wavelength/energy to temperature)

The scale mostly used in sciences, physics and astronomy is Kelvin

The unit is Kelvin (K).

Thermal Radiation

Reference #1

Reference #2

• The fundamental sources of all

electromagnetic radiation (EMR) are

electric charges in accelerated motion

• All bodies emit electromagnetic radiation

as a result of thermal motion of their

molecules This radiation, called thermal

radiation, is a mixture of different

• Thermal radiation is emitted by all objects

above absolute zero (-273.15°); but some

of objects is in visible

An electric heating element emits primarily infrared radiation But if its temperature is high enough, it also emits a discernible amount of

visible light.

What is a Blackbody

A blackbody is an idealized object that

absorbs all EMR that falls on it - no

EMR passes through it and none is

reflected (i.e perfect emitter and

Because no light (visible EMR) is

reflected or transmitted, the object

appears black

Leave appears green because green

color is reflected to human eye