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WAVES

WAVES. Unit 5. SUMUP for general waves. The energy of a wave falls off as the wave moves away from its source. Diffraction takes place when the wavelength of a wave and the size of an obstacle or opening are comparable.

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WAVES

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  1. WAVES Unit 5

  2. SUMUP for general waves • The energy of a wave falls off as the wave moves away from its source. • Diffraction takes place when the wavelength of a wave and the size of an obstacle or opening are comparable. • The amplitude of a mechanical waves determines the energy of mechanical waves. • Transverse waves cause particles to vibrate back and forth, perpendicular to the wave direction.

  3. SUMUP for general waves (cont’d) • Interference occurs when two waves simultaneously arrive to a particular point in space. If the phase difference of the two waves is 0 or a whole number of wavelengths, then the result is constructive interference. A phase difference of 180 results in the waves cancelling each other. A phase difference between 0 and 180 will cause partially destructive interference.

  4. SUMUP for sound waves • Sound waves are longitudinal, mechanical waves. • The Doppler effect is caused by the relative motion between the wave source and the observer.

  5. SUMUP for light waves • Light waves are transverse. • Light slows down, bends toward the normal and has a shorter wavelength when it enters a medium with a higher index of refraction than the medium in which it was previously traveling. • Blue light has more energy (a shorter wavelength and higher frequency) than red light.

  6. SUMUP for light waves, (cont’d) • At the interface of a medium, light can be reflected or refracted. • Lenses and mirrors form images. Different combinations of lenses and mirrors may form real or virtual images. • A photon is a unit of light. • Increasing light intensity on a material increases the number of emitted electrons but not the kinetic energy of the electrons (the photoelectric effect).

  7. SUMUP for EMag waves • Electromagnetic waves are produced by changing the motion of charges or by changing magnetic fields. • The energy of electromagnetic waves is transferred to matter in quantized quantities. • The energy content of electromagnetic waves is directly proportional to the frequency of electromagnetic waves. • Large waves have very short wavelengths when moving and thus cannot be observed behaving as a wave (DeBroglie Principle).

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