Physical Science

Unit 3 Lesson 1- Mechanical Waves   All waves can be classified into two groups: mechanical waves and electromagnetic waves Mechanical Waves: Mechanical waves carry energy through a medium which is a solid, liquid, or a gas, e.g: sound waves carrying energy through the air. Mechanical waves are divided into two groups based on the direction in which the particles vibrate relative to the direction of the energy. They can be grouped into either transverse waves or longitudinal waves. Transverse: These transverse waves vibrate the particles of the medium perpendicular to the direction of the wave. The highest points on a transverse wave are called crests, while the lowest points are called troughs. The distance from one crest to the next crest is referred to as the wavelength. The amplitude of a transverse wave is the distance from a crest, or trough, to the resting position of the wave. The frequency of a transverse wave can also be determined by the number of waves that pass a given point in one second. High frequency waves have crests that are closer together than low frequency waves. The frequency is measured in units called hertz Longitudinal: Longitudinal waves vibrate the particles of the medium in the same direction of the wave. Areas where the particles are closer together are called compressions, and rarefactions are the areas where the particles are farthest apart. The wavelength of a longitudinal wave is measured from one location on a compression to the same location on the next compression. The amplitude is measured by the degree at which the particles are squeezed together at a compression or spread out at the rarefaction. Sound waves are examples of longitudinal waves. Sound waves, like all waves, travel at different speeds through solids, water, and air. The speed of the wave is determined by how far the wave travels in a given time frame   Electromagnetic Waves:  Electromagnetic waves, such as light and radio waves, can travel through matter but can also travel through the vacuum of space. They are caused by changing electric and magnetic fields. When electromagnetic waves travel through matter, they move like transverse waves. Many types of electromagnetic waves make up the electromagnetic spectrum. The electromagnetic spectrum includes radio waves, microwaves, infrared radiation, visible light, ultraviolet light, X-rays, and gamma rays. Radio waves have the longest wavelength and smallest frequency, while gamma rays have the shortest wavelengths and highest frequencies. Electromagnetic waves are used in everyday life. X-rays and gamma rays are used for medical purposes. Radio waves are used for communication, and microwaves are used to cook food. Infrared radiation can also be used to heat objects, while the ultraviolet light from the sun allows life to exist on Earth. In the middle of the spectrum is the visible light you can detect with your eyes. Both electromagnetic and mechanical waves can move energy from one place to another. The various forms and properties of waves are important to the movement of this energy around the world.

Unit 3 Lesson 2- Properties of Mechanical Waves Transverse Waves:  For transverse waves, the particles of the medium vibrate perpendicular to the direction of the wave. As the energy of the wave passes through the medium, particles move slowly up and down from their original position. The particles move farther away from their original position when there is more energy. Higher wave height means higher amplitudes and greater energy. Lower wave height indicates less energy moving through the wave. The wavelength of a transverse wave is the distance from one crest, the highest point of the wave, to the next crest. The greater the distance between each crest, the longer the wavelength. As the wavelength increases, there are fewer wave cycles over time, and, therefore, the frequency of the wave decreases. As the wavelength decreases, the frequency of the wave increases.   Longitudinal Waves: For longitudinal waves, the particles of the medium vibrate parallel to the direction of the wave. As the energy of the wave passes through the medium, the particles compress and then separate as the energy moves through the wave. Less displacement of the particles from the original position means less energy through the wave. This means a lower amplitude wave. More energy causes more displacement of the particles from their original position. The wavelength of a longitudinal wave is the distance from one point on the compression (where the particles are the closest) to the same point on the next compression. The greater the distance between each compression, the longer the wavelength. As the wavelength increases, there are fewer compressions over time, and, therefore, the frequency of the wave decreases. As the wavelength decreases, the frequency of the wave increases (more compressions over time).   Speed of a wave is Speed= Wavelength x Frequency Periodic Motion- Any motion that repeats at regular time intervals Period- The time required for a cycle

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. 

Lesson 6 Unit 3 Electromagnetic Waves-   Electromagnetic Waves- transverse waves consisting of charging electric fields and changing magnetic fields. Electromagnetic waves are different from mechanical waves in how they are produced and how they travel.  How they are produced- They are produced by constantly changing fields. Electric Field in a region of space exerts electric forces on charged particles. They are produced when an electric charge vibrates or accelerates. 

Unit 3 Lesson 8 Behavior of Light-- Sunsets demonstrate the scattering of light as the blue and some of the green colors have scattered and all that your eye detects are yellow, red, and orange Reflection in water by parallel light waves Sunglasses are polarized meaning they filter out horizontal light, reducing glare and improving vision in the sun Mirages are examples of light being reflected Refraction- when light enters a new medium it bends, and this happens because it changes speed when light goes through less dense or more dense objects  Angle of Refraction: the amount the wave bends  Diffraction- the bending and spreading of waves, usually around an object   Notes-- Materials can be transparent, translucent, or opaque Transparent: transparent material transmits light, which means it allows most of the light that strikes to pass through it Ex: windows allowing buildings and trees to be seen or where the water where fish and coral live Translucent: If you can see through a material, but objects look blurry, then the material is translucent. This material scatters light Opaque: Most materials are opaque, which means you cannot see through them. This material either absorbs or reflects all the light that strikes it.    Interactions of Light-- When light strikes a new medium, it can be reflected, absorbed, or transmitted. When light is transmitted, it can be refracted, polarized, or scattered.  Reflection- image is a copy of an object formed by reflected waves of light.  Regular Reflection- occurs when parallel light waves strike a surface and reflect all in the same direction. This happens when light strikes a smooth surface such as a mirror Diffuse Reflection- occurs when parallel light strikes a rough, uneven surface and reflect in many directions    Polarization: light with waves that vibrate in only one plane is polarized light   Scattering- Earth's atmosphere contains many molecules and other tiny particles. These particles can scatter sunlight. Scattering means that light is redirected as it passes through a medium 

Unit 3 Lesson 9 Color-- Rainbows are a result of sunlight reflecting and refracting through raindrops that act like a prism, separating out visible light waves by their wavelengths. Violet and red light refract at sharp angles compared to blue and green light. Thus, as the white light separates, you see all the colors of the rainbow Why do you see different objects as different colors? For instance, why do you see grass as green? You see objects as different colors because some light waves are absorbed while others are reflected. Grass is green because it absorbs red, orange, yellow, blue, indigo, and violet, but reflects green. These green light waves are what your eyes detect, and so you can see grass.  What happens when you mix primary colors of light? When you mix primary colors of light, which are red, green, and blue, you can see all the other colors. Why do you see the primary pigment color yellow? Primary colors are a result of light waves that are reflected and interpreted by your eyes. You can see yellow pigments because it absorbs blue light and reflects red and green light. When these red and green light waves overlap, your brain intercepts them as yellow. The primary pigment colors are cyan, magenta, and yellow.  Dispersion is when white light separates into colors

Unit 3 Lesson 10 Sources of Light--   Incandescent Light- Light bulb that has a wire and lights up when electricity passes through it. Air has been removed from the inside of the light bulb so the light will stay. Light that is produced when it gets hot enough. Fluorescent Lights- Filled with gas that gives off ultraviolet light when electricity passes through it. In a process called fluorescent, a material absorbs light at one wavelength and then emits light at a longer wavelength. Fluorescent light bulbs emit light by causing phosphor to steadily emit protons.  Laser- a device that generates a beam of coherent light. Laser light is emitted when excited atoms of a solid, liquid, or gas emit photons.  Sodium Vapor Light-- As electric current passes through a sodium vapor bulb, it ionizes the gas mixture. The mixture warms up and the heat causes the sodium to change from a solid into a gas.