Wave Interactions Wave Interactions n Sound and light

Wave Interactions

Wave Interactions n Sound and light waves can undergo reflection, refraction, interference and diffraction n Sound and electromagnetic energy is transmitted through waves, which travel in all directions out from the source n Radiant energy exhibits wave behaviors and particle behaviors

Reflection n Occurs when a wave bounces off a surface n The amount of energy in a reflection wave depends on how much energy is absorbed by the surface it hits.

Diffraction n Bending of a wave as a result of the interaction between a wave and the edge of an object. n Speed, frequency and wave length do not change, but direction does. n Example: Light bending around a doorway

Refraction n Bending of a wave as a result of a new medium. n Waves travel at different speeds in different mediums.

Interference n Effect of two or more waves interacting, producing a larger wave, a smaller wave, or no wave at all.

Superposition n Occurs when two or more waves are traveling through the same medium at the same time. n The waves travel through each other but do not affect one another. n After the two waves meet they will continue traveling through the medium as they were before.

Constructive Interference n Two crests or 2 troughs meet and a single wave with maximum amplitude is produced.

Destructive Interference n When a crest meets the trough of another wave and a reduced amplitude is produced.

Doppler Effect n An observed change in frequency when either the wave source or the observer is moving. n Used to tell if storms are coming closer or moving farther away from us by having radar waves reflect off of precipitation. n http: //www. cleanvideosearch. com/media/action/yt/wat ch? video. Id=h 4 On. BYrb. Cj. Y

Light interactions n All types of radiant energy on the electromagnetic spectrum travel at the same speed in a vacuum. n Also, light interacts with different types of materials. n Opaque: When light strikes an opaque object none of it passes through. Most of the light is either reflected by the object or absorbed and converted to heat. Materials such as wood, stone, and metals are opaque to visible light.

Transparent n Transparent: almost all light passes through (transmitted through) n Examples include: water, glass, air

Translucent n When light strikes them, only some of the light passes through them. n The light does not pass directly through the materials. It changes direction and is scattered as it passes through. n We can’t see clearly through them; Because translucent objects are semitransparent, some ultraviolet rays can go through them. n Example: plastics

Smooth Objects n Smooth: angle of incidence equals angle of reflection (fig. 3 pg. 561)

Rough Objects Rough: light waves are reflected in many directions (fig. 3 pg. 561)

Light Models n There are two common models to describe light – light as a wave or as a stream of particles

Light as a wave n Light consists of waves n This model explains many of the basic properties of light and light’s behavior n Evidence that supports the wave model of light – reflection, refraction, diffraction, constructive interference, destructive interference

Light as a particle n Wave model cannot explain some observations n Light can be modeled as a stream of particles (photons) n Photons do not have mass, they are bundles of energy n Energy of photons are located in specific areas n Evidence – dim, blue light knocking electrons off a metal plate