Interference Twosource interference of light Thin films will

Interference

Two-source interference of light

Thin films will interfere • The reflections of the two surfaces in close proximity will interfere as they move from the film. • Figure (b) at right displays an explanation and a photograph of thinfilm interference.

Interference between mechanical and EM waves

Thick films and thin films behave differently

Photons, Electrons, and Atoms • To consider the fundamental increment of light, the photon • To study the removal of an electron by an incident photon, the photoelectric effect • To review the concept that atoms absorb or emit line spectra and have quantized energy levels • To consider the concept of the nuclear atom • To follow the model for an atom set forth by Niels Bohr • To explain how a laser works and different ways lasers are constructed and function • To review x-ray production and x-ray scattering

Line spectra • The light emitted when atoms excited by the electrical energy is released takes the form of distinctly colored lines. These lines will always form the same pattern for a given atom, which is very unlike the behavior of white light.

The photoelectric effect

Atomic line spectra

Hydrogen spectra in more detail

The Bohr model • Classical physics predicts that a moving electron would emit radiation and decay. • Bohr postulated stable orbits at quantized energy levels that did not decay.

The laser • Light amplification by stimulated emission of radiation is what the acronym stands for. It’s very much like a standing wave of light. Excited states will naturally radiate on a timetable appropriate for their states, but a light wave passing an excited state increases the likelihood of radioactive decay.

He. Ne laser • Small semiconducting lasers have sold many millions since the inception of CD and DVD devices among personal electronic equipment, but the He. Ne laser has filled many laser pointers.

X-rays and scattering • Information about the quantum nature of x-rays first came from Compton scattering in 1923.

A Compton experiment

Vocabulary: Photoelectric effect =Fotoelektrik olay Discrete wavelength= ayrık dalgaboyu Diffaraction=kırınım Slit=Yarık Adjustment =ayarlama Initial level=ilk düzey Final level=son düzey Raise=yükseltmek Drop=düşme Ground Level=temel düzey Excited Levels=uyarılmış düzeyler Attraction=çekici Stable=kararlı Unstable=kararsız Interfrence=Girişim Postulate=doğru varsayılan kanıtsız önerme Radioactive decay= radyoaktif bozunma Spontaneous=kendiliğinden, doğal Stimulated=uyarılmış Discharge=desarj Conservation=koruma Coherent=eşevreli, uyumlu, yapışık Constructively=yapıcı Destructively=yıkıcı Bright band=Parlak bant Proximity=yakınlık Thin film=ince film Thick film=kalın film