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            <h1>Waves</h1>
            <span class="subheading">Unit 4</span>
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        <p><b>Waves</b> are a disturbance that transfers energy from one point to another. In 1887, <b>Heinrich Hertz</b> demonstrated his findings on radio waves in his labratory which proved the existence of waves, predicted by <b>James Clerk Maxwell</b>.</p>
        <img class="img-fluid" style="margin-left: 200px;" src="https://cdn.britannica.com/18/1218-004-ECA9F94F/Heinrich-Hertz.jpg">
        <span class="caption text-muted">Heinrich Hertz</span>
        <img style="margin-left: 200px;" src="http://www.astronoo.com/images/biographies/james-clerk-maxwell.jpg" class="img-fluid">
        <span class="caption text-muted">James Clerk Maxwell</span>
        <h1 id="in">Key Terms</h1>
        <p>
          <ul>
            <li>Amplitude: measure of the displacement of the wave from its rest position. The greater the amplitude, the higher its energy and vice versa.</li>
            <li>Crest & Trough: the crest is the highest point on a wave and the trough is the lowest point.</li>
            <li>(λ)Wavelength: the distance between identical parts of a wave(wave cycle).</li>
            <img class="img-fluid" src="img/post-sample-image - 副本 (16).jpg">
            <span class="caption text-muted">Properties of the two waves</span>
            <li>(T)Period: time taken for one complete wave cycle. Measured in seconds/cycle. It is the reciprocal of frequency(T=1/f)</li>
            <li>(f)Frequency: number of occurances of a periodic event per time. Measured in Hz(or cycles/second) and is the reciprocal of period(f=1/T). The pitch of a sound is related to it, the higher the pitch the more frequency and vice versa.</li>
            <li>Medium: a substance or material that can propagate waves or energy.</li>
            <li>Linear Mass Density(kg/m): measure of a quantity of mass per length; density.</li>
            <li>Longitudinal Waves: waves in which the motion of the individual particles of the medium is in a direction parallel to the waves' direction. Thus the particles move back and forth.
              <ul>
                <li>Rarefaction: a section of the Longitudinal Wave where the particles are the furthest from each other.</li>
                <li>Compression: a section of the Longitudinal Wave where the particles are the closest from each other.</li>
              </ul>
            </li>
            <li>Transverse Waves: waves in which the motion of the individual particles of the medium is in a direction perpendicular to the waves' direction. Thus the particles move in a up and down motion.</li>
            <li>Wave Speed: the speed of a wave(how much it travels per second). It can be calculated just like how speed is calculated: <br>v=f * λ<br> =λ/T</li>
            <li>Wave Power: a wave pulse per unit time.</li>
            <li>Oscillation/Vibrates: the repetitive variation of something.</li>
            <li>Equilibrium Position: the position where all forces are balanced, referred as the rest position.</li>
            <li>Mechanical Waves: transfer of energy through a material by particle vibration.</li>
            <li>Shock Wave: wave that consists of a single disturbance(pulse)</li>
          </ul>
        </p>
        <h2>Analysis</h2>
        <p>
          Increasing the amplitude of a wave would mean a bigger displacement from the Equilibrium position, which doesn't affect any of the other properties. A higher amplitude means more energy in the wave. <br>
          For instance, a sound wave from a scream would have a larger amplitude than the sound wave from a whisper because there is more energy exerted in the scream.
          Increasing the frequency of a wave would affect the wavelength and period but not the wave speed because the wave speed is the speed at which the wave is travelling and the frequency is the number of cycles fit into a unit of time. Since there are more cycles that happen each second, the wavelength would have to become smaller and the time for one complete cycle(period) would also have to become smaller.
        <br>Wave speed are however affected by the magnitude of forces. The stronger the foce, the more efficient for the transfer of energy, and the faster the speed and vice versa. Which is why changing the tension force and the linear mass density affects it.
        </p>
        <h1>Particle Behaviour in Different Medias</h1>
        <p>
          When waves pass through a media, the vibrations in solids, liquids, or gases lose very little energy, which is why we are able to hear sounds from a distance even after the wave has the travel through many gases. All particles in a medium are connected by intermolecular forces. A wave is able to efficiently travel through a solid because it has strong intermolecular forces and the energy is able to transfer itself with ease.
          A liquid have a slightly weaker intermolecular structure, so it still has a strong transfer of energy, but a gas has molecules that are much farther apart so energy is transferred less efficiently.
          <img class="img-fluid" src="img/post-sample-image - 副本 (17).jpg">
            <span class="caption text-muted">Particle Behaviour in Solids, Liquids, and Gases</span>
            Waves also travel faster in higher temperatures than in lower temperatures because the particles in the warmer temperatures are much faster than the particles in colder temperatures, even if the colder air is more dense.
        </p>
        <h1>Interference</h1>
        <p>
          Superposition is the result in adding two waves together.
          <ol>
            <li>Constructive Interference is occurs when two "similar" waves superimpose and the resulting wave has a higher amplitude then the previous waves.</li>
            <li>Destructive Interference is when two "opposing" waves superimpose and cancel each other out, leading to little to no amplitude. </li>
          </ol>
          <img class="img-fluid" src="img/post-sample-image - 副本 (20).jpg">
          <span class="caption text-muted">Two Types of Wave Interference</span>
        </p>
        <h1>Sound Waves</h1>
        <p>
          Sound comes from vibrating objects in the form of a Longitudinal wave, and it is a type of wave that can be heard by the human ear. Sound requires a medium to travel through, so sound doesn't exist within a vacuum.<br>
          The speed of sound formula in air can be formulated like so: <br>
          v=331.4m/s + (0.606m/s/C)Temp(C) <br>
          As seen in the formula, the speed of sound varies with the consideration of density and temperature in a medium.
        <h2>Doppler Effect</h2>
        <p>
          The Doppler Effect is when the source of the sound is approaching and the frequency of the sound appears higher than normal, and lower when the source is moving away. We humans perceive this as <b>pitch</b>. <br>
          An example of this is when a loud moving vehicle(e.g. Ambulances, Firetrucks, etc) passes you. They have a high pitch and the waves moves towards the blue end of the electromagnetic spectrum(shorter wavelengths; blueshift) as they approach you, and a low pitch and the waves moves towards the red end of the electromagnetic spectrum(longer wavelength; redshift) as they pass you.
          <img class="img-fluid" src="img/post-sample-image - 副本 (18).jpg">
            <span class="caption text-muted">Doppler Effect</span>
        </p>
        <h2>Mach Speed</h2>
        <p>
          The Mach Speed is a number used to describe the airspeed of an object. It is the ratio between the airspeed of an object and the speed of sound in the medium. If Mach equals 1, then the object is travelling at the speed of sound, if Mach equals 2, the object is travelling at double the speed of sound, and so on. <br>
          An example of this is when an aircraft breaks the sound barrier and exceeds the speed of sound:
          <img class="img-fluid" src="img/post-sample-image - 副本 (19).jpg">
            <span class="caption text-muted">"Breaking the Sound Barrier"</span>
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