Physics - Diffraction of Waves 発表

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🌊 “Diffraction” of Waves

🔍 Examples

📚 Prerequired Knowledges

• Wave front

  • Blue line: “Wave front”

  • Red arrow: “Rays”

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Simulation

• https://www.compadre.org/osp/EJSS/4480/268.htm

🤔 Huygen’s Wave Theory

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• Proposes a new way to understand the movement of wave

• Think that every points on a wavefront are wave sources

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  • These movements can be explained by the theory

Now more mathematical? part -

• Q. How does wavelength $\lambda$and opening of obstacle$w$affect the diffraction?

Q. How does wavelength $\lambda$and opening of obstacle$w$affect the diffraction?

• Diffraction effect is significant when $\frac{\lambda}{w}>1$
  • i.e. When wavelength is comparable or larger than opening
• Generally, diffraction is larger when: lambda is larger than opening

💪 Some questions Q. Why can we hear, but can not see the source behind the wall?

A.

• wavelength of audible sound: 17mm - 17m
• wavelength of visible light: 360nm - 400nm
• wave length of visible light is much smaller than opening
  • –> Almost no diffraction of light Q.
• Hint: Use $c=f\lambda$

A.

Q. Draw the wavefronts of these waves as they emerge through the aperture.

• waves of wavelength 1mm approaching an aperture of size 8mm
• waves of wavelength 1mm approaching an aperture of size 1mm

A.