Unit 3 Lesson 3- Behavior of Waves
Some examples of behavior of waves are reflection and refraction
Reflection--
Reflection is a property common to all waves. Reflection occurs when a wave hits an obstacle and bounces back at the same speed. Note that the obstacle will not be another wave, since waves can pass through each other without incident. The angle at which the wave hits the obstacle is called the angle of incidence. The wave will reflect back at the exact same angle, called the angle of reflection. For example, if a wave hits an obstacle at a 45-degree angle, then the wave will reflect back at 45 degrees.
When reflection occurs, the speed of the wave does not change, and the wave essentially flips over on itself. Reflected waves add to the original waves to form patterns. When waves hit a parabola, they reflect at various angles, making the waves focus at the same point in the center of the parabola
Refraction--
Refraction occurs when a wave enters a new medium at an angle and either speeds up or slows down. For example, when light passes through a glass of water, the light will slow down as it passes from the air into the water. Light travels slower in the denser water, and the light waves bend, or refract.
Refraction causes waves to change direction. For example, if an ocean wave hits shallow water at the shore, the wave begins to bunch up. If the wave hits the shallow water at an angle, the part of the wave that hits first will slow down and then drop behind. This makes the wave swing around and change direction.
Diffraction--
Diffraction is the bending of the wave as it moves around an object or passes through a narrow opening. A wave diffracts more if its wavelength is large compared to the size of an opening or an obstacle.
Interference--
Interference is when two or more waves overlap and combine together. Two types of interference are constructive and destructive interference.
Constructive- happens when two or more waves combine to produce a wave with a larger displacement
Destructive- happens when two or more waves combine to produce a wave with a smaller displacement.
Unit 3 Lesson 4- Sound and Hearing
- True or False: Sound can travel faster through air than it can through water or metal. False. Sound can travel approximately 331 m/s through air; 1,509 m/s through fresh water; and 5,000 m/s depending on the type of metal it is traveling through.
- True or False: Loudness is a subjective measurement, meaning it varies depending on who is hearing the sound. This is true. Loudness varies depending on the individual. Intensity, however, is the power of sound per unit area or the wave's energy in a unit area. This is not subjective, and it is measured in decibels.
- True or False: High frequency sounds have a higher pitch, and low frequency sounds have a lower pitch. This is true. Although pitch can be subjective, it depends on frequency. If something has a high frequency, meaning something is vibrating quickly, it will have a higher pitch or sound like a higher note than something that is vibrating more slowly and has a lower pitch.
These properties can explain sound-
speed, intensity, loudness, frequency, and pitch.
Speed- You hear a delay in echoes because sound has speed and it takes time for these waves to travel.
Sound waves travel fastest in solids, slowest in liquids, and slowest in gases. The speed of sound depends on many factor such as the density of the medium and how elastic the medium is.
Intensity- the rate at which a wave's energy flows through a given area. Sound intensity depends on both the wave's amplitude and the distance from the sound source.
Loudness- a physical response to the intensity of a sound, modified by physical factors.
Frequency depends on how fast the source is vibrating.
Pitch- the frequency of the sound as you hear it
Ultrasound is sound at frequencies higher than most people hear. Sonar is a technique for determining the distance of an object underwater.
