Wave particle duality

 Einstein's explanation on photo electric effect directed scientific approaches about waves to a new directions.Some scientists came up with the idea that, if waves could act as particles, it must be possible for even particles to act as waves. With this idea scientist De Broglie proposed a new equation relating momentum and wavelength.
 
For a particle is having a momentum (P)
 
Wavelength ( λ ) = Plank's constant (h) / Momentum (P)
λ = h / P
Value of this wavelength (λ) is called de Broblie wavelength 
 

Electron diffraction

 De Broglie formulated his hypothesis in 1924. It stated that particles too behave as waves. This was confirmed for electrons three years later by the scientists Lester and Clinton. In their experiments they observed diffraction of a fast beam of electrons after passing through a thin gold foil. They observe changing of diffraction pattern when speed of the electrons were changed. With the readings taken with these diffraction patterns they were able to find debroglie wavelength practically. After studying of electron diffraction patterns scientists accepted that both waves and particles could show dual behavior. This is called wave particle duality.
 
Electron microscope.
 
 
Resolving power of a microscope is limited by the wavelength of light. Wavelength of visible greenlight is 0.55µ while wavelength of an electron beam used in electron microscope is 0.000005µ. This makes sense that instead of visible light using a wave of electrons gives more resolution power . Electron microscope was designed based on this concept.

An electron gun emits electrons, these electrons were accelerated to a desired velocity by an electric field. This velocity is calculated to match the desired wavelength of electron beam. 
Then electron beam is passed through a thin section of specimen, 
After getting passed through specimen electron beam is magnified by magnetic fields in lenses. 
Finally magnified beam is incident on a fluorescent screen, where electron beam produces a magnified image of specimen. 
This whole procedure occurs in transmission electron microscope. The same concept is applied in scanning electron microscope also, but here the electrons do not pass through specimen instead get reflected back from specimen 


 
Congratulations you have just completed all learning outcomes of this lesson as expected in teacher's guide.👌💗 2/7 th of unit Matter and Radiation is covered.
 
• gives evidence about the wave nature of matter.✔️
• accepts that any particle of a specific momentum has an associated wavelength called the de Broglie wavelength.✔️
• applies de Broglie hypothesis for the determination of the de Broglie wavelength of matter waves associated with a moving particle. ✔️
• explains the principle of electron microscope✔️