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Waves. By: Oscar Castellon, Cesar Rodriguez, Diego Rodriguez ,and Alexxa Cruz. Lesson 1: What are waves ?. What are waves ?.
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Waves By: Oscar Castellon, Cesar Rodriguez, Diego Rodriguez ,and Alexxa Cruz
What are waves? • Imagine yourself in a pool. Now your friend makes a super cannonball into the water. What will happen? Immediately all the water in the pool starts moving as waves. Waves is a disturbance that causes energy to travel without moving matter. So through all that waves your friend made traveled energy. A. A Source Of Energy: When a rain drop falling it has energy as it hits the water in a pond, lake or river the energy is transfer to that lake, river or pond. In this case the rain drop is the energy source and one thing very important about waves is that waves transfer energy away from the energy source.
What are waves? B. Energy Transfer In this part we will use the cannonball example again. But this time imagine you are in a raft at the other side of the pool. When your friend hits the water he transfers the energy by waves the waves starts from where the diver landed and travels to where you are. When they reach you, you will start to go up and down. One curious thing about waves is that in the cannonball example after all the waves are finish you still in the same place because waves move the energy without moving matter. C. How waves transfer energy. Again with the diver example, when he hits the water he exerts a force on the water particles. The force of the impact transfers the energy by pulling and pushing water particles. Then those particles push and pull others and it keep going outward the impact until it reaches you.
MechanicalWaves • A water wave is a mechanical waves. Mechanical wave is a wave that can only travel through matter. This waves can travel through liquid, solid, and gases. Medium is the material in which the wave travels. There are two types of mechanical waves transverse and longitudinal. A. Transverse Waves When you shake a rope up and down really fast you can create a wave, a transverse wave. A transverse wave is a wave in which the disturbance is perpendicular to the direction the wave travels. When you move the rope up and down it has high and low points. The crest is the highest point in a transverse wave, and the trough is the lowest point in a transverse wave.
Mechanicalwaves B. Longitudal Waves A longitudal wave makes the medium move parallel to the direction of the wave. A spring or “slinky” can show you a longitudal wave. In this wave instead going up and down the particles get closer then apart and those two parts of the wave have names. The compression is the part of the wave were the medium particle are close together, and rarefaction is the part of the wave were the particle are far apart. C. Vibrations and Mechanical Waves Vibrating objects produce mechanical waves. When you have a rope and move your hand up and down just one time it is a single vibration and it makes a transverse wave with one crest and one trough. By pulling and pushing a spring once you create a longitude wave with one vibration and it has one compression and one rarefaction. When you move your hand up and down several times with the rope you transfer enough energy to stop moving your hand and the waves will still traveling.
Types of Mechanical Waves There are three type of mechanical wave water wave, sound wave, and seismic wave. A. Water Waves These waves are combinations of transverse and longitudal waves. Most waves are formed by wind. B. Sound Waves Are longitudal waves that can travel in liquid, solid or gas. Speakers can produce sound wave because of a paper cone inside them that produces compressions and rarefactions. C. Seismic Wave These are mechanical waves that travel in earth surface and cause earthquake. There transverse and longitudal seismic waves. Faults in earth’s crust can cause seismic wave.
Electro Magnetic Waves Light travels from the sun to earth in a wave but not a mechanical wave but a electromagnetic wave. An electromagnetic wave is a wave that can travel through empty space and matter. A. Types of Electromagnetic Waves Another types or electromagnetic waves are light waves, microwaves, infrared waves, radio waves and ultraviolet rays. Cell phones use microwave and sun throws ultraviolet rays that can cause you sunburn. B. Electromagnetic Waves and Objects Every object gives electromagnetic waves including you, you release infrared waves and a piece of glowing metal may release light waves. C. Electromagnetic Wave From the Sun Like all waves, electromagnetic waves carry energy. Scientists often call this radiant energy. Infrared and visible light waves carry about 92 percent of radiant energy that reaches earth from the sun. Ultraviolet rays carry about 7 percent of the sun’s energy.
Amplitude and energy Amplitude: It is the maximum distance that a wave moves from its resting point. For any wave the larger the amplitude, the more energy it carries. • Amplitude and Energy Transfer of Waves 1. For a transverse wave, the greatest distance a particle can moves from the resting position is to the top of a crest or to the bottom of a trough. 2. The smaller the amplitude, less energy it carries. While the larger the amplitude, the more energy it carries.
Amplitude and Energy • Amplitude and Energy of Longitudinal Waves 1. The amplitude of a longitudinal wave depends on the distance between particles in the compressions and rarefactions. 3. When the amplitude of a longitudinal wave increases , the particles in the medium get closer together in compressions and farther apart in rarefactions. 2. Just as for transfer waves, the energy carried by a longitudinal wave increases as its amplitude increases.
Wavelength Wavelength: Is the distance from one point on a wave to the same point to the next wave. • To measure the wavelength of a transverse wave, you can measure the distance from one crest to the next crest or from one trough to the next trough. • To measure the wavelength of a longitudinal wave, you can measure the distance from one compression to the next compression or from one rarefaction. • Wave length is measured in meters.
Frequency • Frequency: Is the number of wavelengths that pass by a point each second. Frequency is related to how rapidly the object or material producing the wave vibrates. Each vibration equals one wave. • Unit for Frequency: 1. The SI unit for frequency is hertz (Hz). The unit of Hz is the same of 1/s. • Wavelength and Frequency: 1. T0 calculate the wave frequency, divide the number of wavelengths by the time.
Wave speed • Wave speed through different materials Mechanical waves, such as sound waves, usually travel fastest through solids and slowest through gases. Mechanical waves also travel faster as the temperature of the medium increases. Unlike mechanical waves, electromagnetic waves move fastest in empty space and slowest in solids. • Calculating wave speed The symbol for wavelength is called lambda. Wave speed equation Wave speed (in m/s) = frequency in (Hz) x wave length (in m) s=fλ
Waves • Waves interact with matter in several ways. • Waves can be reflected by matter or they can change direction when they travel from one material to another. • When two different overlap a new wave forms, and this new wave has different properties from either original wave.
The Hubble • The Hubble orbits earth collecting light waves before they enter earth’s atmosphere. • Photos taken with the Hubble are clearer than photos taken with telescopes on Earth’s surface. • This is because light waves strike the telescope before they interact with matter in Earth’s atmosphere.
Absorption • Absorption is the transfer of energy by a wave to the medium through which it travels. • Also the amount of energy absorbed depends on the type of wave and the material in which it moves. • All materials absorb electromagnetic waves although some materials absorb.
The law of Reflection • The law of reflection when a wave is reflected from a surface the angle of reflection is equal to the angle of incidence.
Refraction • Sometimes, waves change directions even if they aren’t reflected from a surface. The speed of light waves in water is three fourths the speed of light in the air. When waves slow down they change direction, this is why, when you put a light-stick or a “bendy-straw” it looks like it is bended more than usual. This is called refraction. Refraction is the change in direction of a wave that happens/occurs as the wave changes speed when moving from one medium to another. The greater the change in speed the more the wave changes it’s direction.
Diffraction • Waves can also change direction as they travel by objects. You heard it because the waves changed direction and spread out. The change in direction of a wave when it travels through and object, its edge, or and opening is called diffraction. Diffraction causes water to travel through openings and edges of objects. Depending on the size of the opening or object, more diffraction can be caused. The wavelengths of sound waves are similar in size to many common objects. The wavelengths of light waves are more than a million times smaller than the width of a doorway. As a result, light waves do not spread out as they travel through objects.
Interference When waves meet, they overlap for a while as they travel through each other. This is called interference. Interference occurs when waves that overlap combine, forming a whole NEW wave! However, after the waves travel through each other, they keep moving without having been changed. As waves travel through each other, sometimes, the crests of both waves overlap. A new wave form, with a longer distance than both of the original ones. This is interference is called constructive interference. Deconstructive interference occurs when the crest of one wave overlaps through another wave. The new wave is smaller in amplitude than the sum of the amplitude of both waves. If the two have the same amplitude, they cancel each other when their crests overlap.
References • ConnectED.com
