Page 241 - Physics Form 5 KSSM_Neat

In 1927, the presence of wave properties of electrons was confirmed through electron CHAPTER 7
diffraction experiments. Photograph 7.2 shows the diffraction pattern of electrons through a
thin layer of graphite. This pattern resembles the light diffraction pattern through an aperture as
shown in Photograph 7.3. This confirmed de Broglie's hypothesis. Quantum Physics

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Photograph 7.2 Diffraction pattern of Photograph 7.3 Diffraction pattern of
electrons through a thin layer of graphite red laser light through an aperture
The de Broglie wavelength of an electron beam is approximately 1000 – 10 000 times
shorter compared to the wavelength of light. This property is very important for higher
magnification of electron microscope. A comparison between the images produced by an
optical microscope and an electron microscope is shown in Photograph 7.4.

(a) Image of red blood (b) Image of red blood
cells under an cells under an
optical microscope electron microscope

Photograph 7.4 A comparison between the images produced
by an optical microscope and an electron microscope

LS 7.1.3 231