Wave Properties

S8P4. Students will explore the wave nature of sound and electromagnetic radiation. d. Describe how the behavior of waves is affected by medium (such as air, water, solids). e. Relate the properties of sound to everyday experiences. f. Diagram the parts of the wave and explain how the parts are affected by changes in amplitude and pitch.

Wave Energy Wavelength is the distance between two successive and comparable points on a wave. –The transverse wavelength is the distance between two successive crests or two successive troughs. –The wavelength of a longitudinal wave is the distance between two adjacent compressions or rarefactions.

Wave Energy Amplitude is a measure of wave energy –Amplitude is related to the distance between the crest (high point of a wave) or the trough (low point of a wave) and the wave’s resting position. –The larger the amplitude the taller the wave, and the more energy it carries.

The amplitude of a transverse wave is determined by the height of the crest or depth of the trough

Wave Energy The frequency of a wave is the number of wavelengths that pass by a point each second. Frequency is measured in units of hertz (Hz).

Period Period refers to the number of cycles as a result of time. The amount of time it takes for a wave to complete one full cycle.

Pitch Pitch refers to the highness or lowness of a sound. Pitch depends on how fast the source of the sound is vibrating To change the pitch: –Change the length of the material vibrating –Change the thickness of the material vibrating - - Low pitch - - Low frequency - - Longer wavelength - - High pitch - - High frequency - - Shorter wavelength

Wave Speed The speed at which a wave travels is called wave speed. Wave speed is measured in two ways –1 st Time how long a wave takes to get from point A to point B –2 nd Calculate wave speed by using the following formula: Speed = Wavelength X Frequency

Behavior of Light Waves

Waves do not always travel in one direction. Often they bounce off one surface and then travel in another direction. When any type of wave hits an obstacle or passes from one medium to another, it is possible that the wave will change in speed, direction, or shape.

Behavior of Light Waves Reflection occurs when a wave bounces back after striking a barrier.

Wave Reflection When a sound wave reflects from a surface we generate an echo Wave reflection from surfaces depends on the characteristics of the surface Smooth hard surfaces reflect best Rough soft surfaces reflect poorly Energy not reflected is absorbed or transmitted through the material

Wave Reflection Think of arrows pointing in the direction of the wave motion We can trace the path of these arrows Angles Equal

Refraction is the bending of a wave as it passes at an angle from one medium to another. The break in the pencil appears because the light waves bend as they pass from the air into the water. This bending occurs because the air and the water have different densities. Refraction of light takes place when light passes from a medium having one density to a medium with a different density. Behavior of Light Waves

Wave Refraction

Behavior of Light Waves Diffraction refers to the bending, spreading, and interference of waves when they go through a narrow opening. Diffraction occurs with any type, including sound waves, water waves, and electromagnetic waves. Diffraction is light passing through a slit that is very narrow, smaller than the wavelength of the light wave. After the wave passes through the slit, a pattern of ripples form in all directions, as if there were a wave source right at the position of the slit itself.

Behavior of Light Waves Diffraction can also be detected when the slit is wider than the wavelength. When the slit is more than a wavelength wide, there is a diffraction pattern that occurs right at the edges of the wave. The center part of the wave travels unaffected at short distances, but the diffraction at the edges will cause a diffraction pattern when observed from longer distances.

Behavior of Light Waves Transmission is the passing of waves through a medium. A radio wave is a type of electromagnetic wave produced at the radio station. The wave travels from the station's transmitter out in all directions at the speed of light.

Behavior of Light Waves Absorption is the disappearance of an electromagnetic wave into a medium. It is the opposite of reflection. You see different colors because of the selective absorption of visible light.

Behavior of Light Waves Some materials absorb all wavelengths of visible light. A material that absorbs all wavelengths of visible light appears black. By contrast, a material that reflects all wavelengths of visible light appears white.