Academic Standard 8-6 Topic: Waves
8-6 The student will demonstrate an understanding of the properties and behaviors of waves. (Physical Science)
Key Concepts
Waves: matter vs. energy, mechanical vs. electromagnetic
Wave properties: frequency, amplitude, wavelength, speed
Wave behaviors: refraction, reflection, transmission, and absorption
Hearing: sound waves, ear structure
Sight: eye structure, light waves emitted or reflected
Color: absorption and reflection of light waves
Electromagnetic spectrum: wave energy, wavelengths, visible light, infrared & ultraviolet radiation
Indicators:
8-6.1 Recall that waves transmit energy but not matter.
Taxonomy level: 1.2-B Remember Conceptual Knowledge
Previous/Future knowledge: Students have been introduced to the concept of energy in 1st grade related to plants (1-2.1), related to animals in 2nd grade (2-2.1), to light and electricity as forms of energy in 4th grade (4-5.2); and to forms and transformations of energy in 6th grade (6-5.2). Students have not been introduced to the concept of energy being transmitted in waves in previous grades. Students will further develop the quantitative concepts energy transmission in waves in 9th grade Physical Science (PS-7.3 and PS-7.4).
It is essential for students to know that energy is the ability to cause something to happen or change and that a wave is a repeating disturbance, vibration, or movement that transfers or moves energy from place to place. Waves carry energy through empty space or a medium (material through which waves can travel) without transporting matter.
It is not essential for students to know that quantitative relationship between energy and waves.
Assessment Guidelines:
The objective of this indicator is to recall that energy, not matter, is moved from place to place by waves; therefore, the primary focus of assessment should be to retrieve from memory information about waves as vibrations that transfer energy. However, appropriate assessments should also require students to recall the definition of waves, energy, or medium and that waves transfer energy not matter.
8-6.2 Distinguish between mechanical and electromagnetic waves.
Taxonomy level: 4.1-B Apply Conceptual Knowledge
Previous/Future knowledge: Students have not been introduced to the concept of mechanical and electromagnetic waves in previous grades. Students will further develop the concepts of different types of waves in high school Physical Science (PS-7.1-2).
It is essential for students to know the following characteristics of mechanical and electromagnetic waves:
Mechanical
waves Mechanical waves are waves that travel through matter. The matter that waves travel through is called a medium and it can be a solid, liquid or gas, or a combination of these. The particles of matter vibrate by pushing together and moving apart, or by moving up and down, as the waves travel through them to transfer the energy through the medium. Sound waves, for example, are mechanical waves that require particles to vibrate in order for energy to be transferred. Sound waves cannot be transferred or transmitted through space. Water waves and the waves that travel down a rope or spring are also mechanical waves.
Electromagnetic
waves Electromagnetic waves are waves that can travel through empty space where matter is not present. Instead of transferring energy from particle to particle as is done by mechanical waves, electromagnetic waves transfer energy through space. Radio waves, microwaves, infrared rays, visible light, ultraviolet rays and x-rays are all forms of energy that travel in electromagnetic waves.
It is not essential for students to know that electromagnetic waves are caused by vibrating electric charges, or that they transfer energy between vibrating electric and magnetic fields.
Assessment Guidelines:
The objective of this indicator is to distinguish between electromagnetic and mechanical waves; therefore, the primary focus of assessment should be to differentiate between electromagnetic and mechanical waves. However, appropriate assessments should require students to recall definitions of electromagnetic and mechanical waves; or to classify waves as mechanical or electromagnetic based on their characteristics.
8-6.3. Summarize factors that influence the basic properties of waves (including frequency, amplitude, wavelength, and speed).
Taxonomy level: 2.4-B Understand Conceptual Knowledge
Previous/Future knowledge: Students have not been introduced the concept of waves in previous grade levels. Students will further develop the concepts of waves quantitatively in 9th grade Physical Science (PS-7.4)
It is essential for students to know the basic properties of waves and factors that influence them as follows:
Wavelength Wavelength is the distance between one point on a wave and the nearest point just like it. The wavelength is the measure of the distance between any two successive identical parts of wave. The greater the energy carried by waves, the smaller the wavelength.
Frequency Frequency is the number of full wavelengths that pass a point each second. The frequency of a wave also measures how rapidly vibrations occur in the medium, at the source of the wave, or both. The greater the energy carried by waves, the greater the frequency.
Amplitude Amplitude is the greatest distance that vibrations in a wave move from their normal position when a wave passes by. The greater the wave’s amplitude, the more energy the wave carries.
Speed Speed is the distance per time that a given wave travels. A particular type of wave has a wave speed that is constant in a specific medium or in space. As a wave enters a different medium, the wave’s speed changes. Waves travel at different speeds in different mediums. All electromagnetic waves travel at the same speed in empty space—300 million m/sec.
It is not essential for students to know the quantitative relationships among these wave properties or the factors that influence them.
Assessment Guidelines:
The objective of this indicator is to summarize the factors that influence the basic properties of waves; therefore, the primary focus of assessment should be generalize major points about how properties of waves are influenced by various factors. However, appropriate assessments should also require students to recognize the basic properties of waves and how they are related to the factors that affect them; or interpret or illustrate diagrams of waves by identifying specific characteristics state previously.
8-6.4 Summarize the behaviors of waves (including refraction, reflection, transmission, and absorption).
Taxonomy level: 2.4-B Understand Conceptual Knowledge
Previous/Future knowledge: Students have been introduced to the concepts of refraction, reflection, and absorption in 4th grade (4-5.3) Students have not been introduced to the concept transmission in previous grade levels. Students will further develop the concept of the behavior of waves in 9th grade Physical Science (PS-7.6).
It is essential for students to know that waves have the following behaviors:
Refraction Refraction is the bending of waves caused by a change in their speed as they pass from one medium to another. As waves pass at an angle from one medium to another, they may speed up or slow down. The greater the change in speed, the more the waves bend. Refraction of light going from air through a convex lens, for example, can make images appear larger as the light waves bend. Prisms separate white light into its different components or colors by bending the light at different angles depending on the wavelength of the light passing through the prism. Different wavelengths of light travel at different speeds in a given medium.
Reflection Reflection is the bouncing back of a wave when it meets a surface or boundary that does not absorb the entire wave’s energy. All types of waves can be reflected. Reflections of sound waves, for example, are called echoes and help bats and dolphins learn about their environments. Mirrors and other smooth surfaces reflect light to form clear images.
Transmission Transmission of waves occurs when they pass through a given point or medium. Light waves are transmitted by transparent materials that allow most of the light that strikes them to pass through them. Only a small amount of light is reflected or absorbed.
Absorption Absorption of waves occurs when the energy is not transferred through the given medium or space. Absorption of waves causes the following behaviors depending on what type of wave is absorbed:
· Color The color of the object depends on the light wavelengths that are absorbed and reflected. Substances that absorb certain wavelengths of light reflect other wavelengths and have specific colors that are characteristics of that substance. Color filters allow only certain colors of light to pass/transmit through them; they absorb, or reflect, all other colors.
· Temperature
change Objects or substances that absorb infrared radiation become warmer as the infrared radiation is transformed to thermal (heat) energy by causing particles in the substance to move at a faster rate.
It is not essential for students to know the quantitative relationships in refraction, reflection, absorption, or transmission of waves.
Assessment Guidelines:
The objective of this indicator is to summarize the behaviors of waves; therefore, the primary focus of assessment should be to generalize major points about the interactions of waves based on the characteristics of waves. However, appropriate assessments should also require students to recognize the behaviors of waves and to exemplify the behaviors of waves based on descriptions of these behaviors; to interpret or illustrate diagrams of waves by recognizing behaviors that are illustrated; or to explain the major effects of wave behavior.
8-6.5 Explain hearing in terms of the relationship between sound waves and the ear.
Taxonomy level: 2.7-B Understand Conceptual Knowledge
Previous/Future knowledge: Students have been introduced to the concept of sound as vibrations in 3rd grade (3-5.5). Students have not been introduced to the concepts of sound waves or their interactions with the ear in previous grades. Students will further develop the concepts of sound waves in 9th grade Physical Science (PS-7.7).
It is essential for students to know the relationship between the three main parts of the ear and sound waves to explain hearing as follows:
Outer ear Sound waves are gathered by the outer ear made up of the ear, the ear canal, and the eardrum. The outer ear is shaped to help capture the sound waves (energy transferred in particles of air) and send them to the ear canal, which transfers them to the eardrum. The vibrations of air particles cause the eardrum to vibrate.
Middle ear The middle ear amplifies sound waves.
Inner ear The inner ear transmits vibrations from the bones of the middle ear to the liquid in the inner ear. The tiny hairs in the inner ear vibrate as the liquid vibrates. The vibrating tiny hairs transmit the energy to nerves attached to the hairs. The nerve impulses are transmitted to the brain for connections in the brain for understanding of the sound as “hearing.”
It is not essential for students to know how each specific part of the three main parts of the ear transfer sound waves for hearing to occur.
Assessment Guidelines
The objective of this indicator is to explain hearing in terms of the relationship between sound waves and the ear; therefore, the primary focus of assessment should be to develop cause and effect models that show the functions of the three main parts of the ear and how they transmit and transfer sound waves for hearing to occur in the brain. However, appropriate assessments should also require students to recognize the three major parts of the ear; to summarize how the major parts of the ear transfer sound waves to the brain for interpretation; or to interpret a diagram of the three major parts of the ear that depicts how sound is transferred and transmitted at each part.
8-6.6 Explain sight in terms of the relationship between the eye and the light waves emitted or reflected by an object.
Taxonomy level: 2.7-B Understand Conceptual Knowledge
Previous/Future knowledge: Students have not been introduced to the concept of the relationship between the eye and light waves in previous grades. They will further develop the concept of light in 9th grade Physical Science (PS-7.6).
It is essential for students to know that the interaction between the major parts of the eye and light emitted or reflected by an object to allow sight to occur as follows:
Cornea The cornea is a transparent tissue that transmits and refracts light to the pupil, the opening in the iris of the eye in front of the lens.
Lens The lens refracts the light further and focuses the light waves on the retina.
Retina The retina is located on the back of the inside of the eye and is composed of tiny nerves that transfer the energy of the light waves to nerve impulses transmitted to the brain for interpretation as sight.
It is not essential for students to know how each of the parts of the main parts of the eye function to interact with light emitted or reflected by an object.
Assessment Guidelines:
The objective of this indicator is to explain how the major parts of the eye interact with light waves to allow sight to occur; therefore, the primary focus of assessment should be to construct cause and effect models of the various parts of the eye indicating how they interact with light waves to allow sight to occur. However, appropriate assessments should also require students to recognize the functions of the major parts of the eye in interacting with light to allow sight to occur; to interpret a diagram of the major parts eye and their functions in transmitting and transferring light to nerve impulses in the brain for sight; or to summarize the transfer of light through the major parts of the eye.
8-6.7 Explain how the absorption and reflection of light waves by various materials result in the human perception of color.
Taxonomy level: 2.7-B Understand Conceptual Understanding
Previous/Future knowledge: Students have been introduced to the concept of color (4-5.2) and absorption and reflection of light (4-5.3) in 4th grade. Students have not been introduced to concept of the human perception of color in previous grades. Students will further develop the concepts of reflection and interference of light waves in 9th grade Physical Science (PS-7.6).
It is essential for students to know that the absorption and reflection of light waves by various materials results in human perception of color as follows:
Reflection Reflection of certain wavelengths of light by various materials causes those materials to appear as a certain color to humans. The color of materials depends on the wavelengths of light that are reflected by various materials and received by the eye. Certain nerves in the eye are sensitive to certain wavelengths of light these nerves transmit signals to the brain, where it is interpreted as color.