<h1>Light</h1>
<ul>
<li>Can act as a particle or a wave (<a href="/second-brain/wave-particle-duality">wave-particle duality</a>)</li>
<li><a href="/second-brain/wavelength">Wavelength</a>
<ul>
<li><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>λ</mi></mrow><annotation encoding="application/x-tex">\lambda</annotation></semantics></math>λ</li>
<li>Distance between two successive crests</li>
<li>Determines colour</li>
</ul>
</li>
<li>Frequency
<ul>
<li><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>f</mi></mrow><annotation encoding="application/x-tex">f</annotation></semantics></math>f</li>
<li>Herz</li>
<li>Cycles per unit of time</li>
</ul>
</li>
<li>Speed
<ul>
<li><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>c</mi><mtext>  </mtext><mo>=</mo><mi>λ</mi><mi>f</mi></mrow><annotation encoding="application/x-tex">c \; = \lambda f</annotation></semantics></math>c=λf</li>
<li>Light travels at <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mn>3</mn><mi>x</mi><mn>1</mn><msup><mn>0</mn><mn>8</mn></msup><mi>m</mi><mi mathvariant="normal">/</mi><mi>s</mi></mrow><annotation encoding="application/x-tex">3 x 10^8 m/s</annotation></semantics></math>3x108m/s</li>
</ul>
</li>
<li>Light is additive</li>
</ul>
<h2>Visible Light</h2>
<ul>
<li>Part of <a href="/second-brain/electromagnetic-spectrum">electromagnetic spectrum</a> to which our eyes are sensitive</li>
<li>What humans can see</li>
<li>ROYGBIV (large --> small <a href="/second-brain/wavelength">wavelength</a>)
<ul>
<li>Violet</li>
<li>Indigo</li>
<li>Blue</li>
<li>Green</li>
<li>Yellow</li>
<li>Orange</li>
<li>Red</li>
</ul>
</li>
</ul>
<h2>Speed of Light</h2>
<ul>
<li><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mn>3</mn><mo>×</mo><mn>1</mn><msup><mn>0</mn><mn>5</mn></msup><mi>k</mi><mi>m</mi><mi mathvariant="normal">/</mi><mi>s</mi></mrow><annotation encoding="application/x-tex">3 \times 10^5 km/s</annotation></semantics></math>3×105km/s</li>
<li>First sign that light's speed was finite came in <a href="/second-brain/1675">1675</a>
<ul>
<li><a href="/second-brain/ole-r%C3%B8mer">Ole Rømer</a> observed <a href="/second-brain/eclipse">eclipse</a>s of <a href="/second-brain/jupiter">Jupiter</a>'s moons
<ul>
<li>Noticed the <a href="/second-brain/eclipse">eclipse</a>s happened earlier/later than predicted at opposition/conjunction</li>
<li>Since the distance between opposition/conjunction is different, speed of light must be have an impact</li>
</ul>
</li>
</ul>
</li>
<li>Takes ~8.3 minutes for light to get from the <a href="/second-brain/sun">Sun</a> to <a href="/second-brain/earth">Earth</a>
<ul>
<li>1 AU --> takes light 8 minutes to travel</li>
</ul>
</li>
</ul>
<a href="/second-brain/physics">Physics</a>

Light

Visible Light

Speed of Light

Backlinks