Light WavesLight Waves

1.1. HUYGENS' PRINCIPLEHUYGENS' PRINCIPLE

Every point on a wave front can be regarded as a new source of wavelets, which combine to produce the next wave front, whose points are sources of further wavelets, and so on.

Huygen’s Principle can be used to explain the propagation of wave

fronts involved in reflection, refraction, and diffraction.

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Consider several points on the wave front

to be sources of secondary wavelets.

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2.2. DIFFRACTIONDIFFRACTION

The bending of light that passes around an obstacle or through a narrow slit, causing the light to spread and to produce light and dark fringes.

Demo - Laser, diffraction accessories, and Demo - Laser, diffraction accessories, and rainbow disks rainbow disks

If the wavelength of water waves are small

compared to the size of an ocean vessel, the

vessel will cast a “shadow.”

For the same waves a stick will not cast a

“shadow.”

Long wavelengths bend a great deal around small objects.

Because of diffraction AM radio waves travel farther than FM radio waves.

Microscopy diffraction limit -

One cannot see details of objects that are approximately the same size as or smaller than the wavelength of the illuminating light.

AM band radio waves travel farther than FM band radio waves because

(a) AM waves travel faster than FM waves(b) AM wavelengths are shorter than FM

wavelengths(c) AM waves are scattered more than FM

waves(d) AM waves are diffracted more than FM

waves

(d) AM waves are diffracted more than FM waves

If laser light passes by a hair, a pattern of light and dark can be seen on a properly placed screen. What phenomenon (phenomena) is (are) being observed?

(a) diffraction

(b) polarization

(c) chromatic aberration

(d) all of the above

(e) none of the above

(a) diffraction