2. Agenda Reason for light of all subjects What is it Scientists that contributed to the discovery of the information of light Light in nature- Sun and star Light bulb Colours in light Lasers Credits
3. Reason for light Since we would be doing things about reflections next term, I thought getting to know about light, the thing that causes reflection. Even if this doesn’t help in it, its not a bad thing to learn more anyway.
4. What is light Layman’s term : the thing that comes out of the light bulb To put it more scientifically, light is made up of photons. Billions of photons They never sit still and they zigzag tens of billions of times a second to form light waves. Hence light = billions of atoms called photons zigzagging their way a billion times to form light waves
6. Scientist Before going into the famous scientist, here is the list of scientist that constantly work with light.
7. Physicists Interested in: physical forces that shape the world- stuff like heat and electricity. One that specializes in light would be a optical physicist. What they do: make calculations about the speed of light and set up light experiments Where they work: university laboratories
8. Astronomers Interested in: stars and planets. Basically stuff in outer space. They are interested in light as that is what enables them to see space objects What they do: scan the night sky using telescopes Where they work: observatories
9. Ophthalmologists Interested in: eyeballs, their diseases and how they work. This is included since light is needed for the eyes to work. What they do: doctors that train patients with eye problems Where they work: hospital eye departments
11. Isaac Newton Though he was famous for the discovery of gravity, he did contribute the research on light. What he did : He was the first man to prove that colours are part of sunlight. He was also the first person to describe seven colours in light but there are actually more. He liked the idea of seven colours as it reminded him of the seven notes in music.
12. Thomas Young What he did: He was the first person to find out that light takes the form of light waves. This was quite an achievement for someone that lived in 1773-1829 . Technology wasn’t as advanced then After him, the were people that continued to prove his theory with math (eg. French physicist Augustin Jean Fresnel)
13. Albert Einstein He was best know for his theories of relativity in 1905 and 1915. He was the man that used pure math to calculate that light was made up of photons. Even though he wasn’t the one that thought up of the idea of light being made up of photons, he was the first man that was able to confirm it.
14. Albert Einstein/Max Planck His work of math to support the fact that photon was part of the light was actually thought up by a German physicist, Max Planck Max said that light was actually made of blips of energy called quanta. His figures explained how energy of light can be turned into heat inside a black box But the only way his calculations added up was if light comes in quanta
15. Albert Einstein/Max Planck Now these quanta are called photons. Albert Einstein was famous as he was the one that was able to successfully confirm the fact that light was made up of photons which Max Planck was unable to do.
16. Light in nature As everyone knows the main source of light we get in nature would be the sun.
17. Sun - some facts The sun is currently in the middle of it’s life. It is currently 4.5billion years old The center of it is 14000000 degrees celcius Light photons are produced by atoms as they are fused together Though we may think of this as a ‘great star’ or something, it is actually just another star
18. Sun - importance Life on Earth depends on the sun for life Hence, no sun = no life This is basically due to the food chain: Sun -> plant -> cow (example) -> human* *using human so we are able to see how the sun affects us
19. Sun - eclipses One dramatic effect of the sun is called an eclipse Caused by the moon getting in the way of the sun Though it has no effect on us except that we would have no sunlight for a few minutes, some people thought otherwise (continued)
20. Sun - eclipses Here are some examples where people went crazy over eclipses. According to Greek writer Thucydides, an eclipse halted a battle between two armies. They agreed to continue after the ‘magical’ effects had worn off In Ancient China, the Chinese beat gongs and pans to scare away the dragon that they thought was eating up the sun.
21. Sun - eclipses 3. The North Americans fired flamed arrows at the sky to re-light the sun. 4. The Pampas tribe of South America believed the moon goddess was darkened in an eclipse with her own blood drawn by savage dogs. As we all know, they were barking up the wrong tree 5. Tartar tribes believed that the sun and the moon were being swallowed up by blood sucking vampires.
22. Stars - starlight Stars as we all know give out light We have to remember that stars are actually very far away. The sun’s light takes 8.5 minutes to reach us. Even our closest star neighbor, Alpha Centauri takes 4 years to arrive to us.
23. Star - starlight The stars we see in the sky are normally : Bluish white Red star The stars are, respectively, around 30000 Degrees Celsius and 2000 Degrees Celsius each (and 2000 is considered cool).
24. Star - starlight Most of you have heard the poem, ‘Twinkle Twinkle little star’ but have you wondered why it twinkles? As the wind blows, the atoms that make up the air may get more crowded in one area than other. As light passes through this area, the light refracts, producing a twinkling effect
25. Light Bulb This is important to light as it was the first man made device that gave out light (with the help of electricity) And as we all know, the light bulb was made by Thomas Edison The history of artificial goes as such Candle->paraffin candle->arc light-> gaslight -> modern day light
26. Light bulb As we all know, Thomas Edison went through 5,999 tries to get the correct items to make the light bulb Some of the failed items included: Platinum wires Rubber Fishing lines Human hair
27. Light bulb The inspiration to think up of the correct material to suddenly came to Thomas Edison’s mind. This inspiration would be : Burnt cotton thread that turned into carbon. This was because carbon only burns at temperatures of about 3500 degrees celcius. It took him three tries to make this special carbon as it was VERY fragile.
28. Colours in light Basic facts: White light contains all the colours in the rainbow. In fact, each colour is caused by a light wave of a particular size. When light hits an object, some colours are being soaked up and some are being reflected. The reflected light is the one that we see.
29. Manipulation of light Manipulation was used as I could not think of any other better word. Anyway the point I would like to put across would be colours appearing as different colours under certain light. The best example for this would be sodium lights
30. Colours – Sodium lights In this light, red things (lipstick, blood or even a red car) appear black. Reason would be because sodium lights contains no red light. Hence because red objects cant reflect any red light we see them as black.
31. Colours – reflected in nature A common example would be the sky. Why is it blue? A scientist would answer : A visible electromagnet wavelength is due to the random deviation of photons by atomic particles. To simplify that: Blue light photons have more energy than others. They are likely to bounce off the atoms downwards and into our eyes. Hence we get to see blue light photons when we look at the sky.
32. Lasers Laser was first appeared in a form of inspiration for an American man ‘Charles H. Townes’ . His idea was to produce a ‘high powered radio wave that can be used to study the structure of atoms’ One day, this was what he thought of (continued)
33. Lasers Heat up atoms Heated up atoms give out radio waves Stop the radio waves escaping until they form a high powered beam (end product) However, in the end, he realised that light could be used instead of radio waves.
34. Lasers For scientist during Townes time, building a laser seemed to prove to be a big challenge In 1960, the first laser was produced, based on Townes’s plans, by US physicist Theodore Maiman.
35. Lasers – current use Lasers are used to cut objects. They can cut fabric at 15m per second Laser beams read bar codes on items bought from various shopping stalls Lasers can cut through human flesh and seal the edges of wounds so you don’t bleed. A laser beam ‘reads’ a CD by flickering as it reflects off a pattern of pits on the CD’s surface
36. Lasers – current use Lasers can be used to cut nice straight tunnels as they travel in straight lines A laser beam can melt and weld metals Laser beams can liven up a pop concert Lasers can also measure tiny earthquakes
37. Credits Information : Frightening light – Nick Arnold/ Tony De Saulles Information : Wikipedia Information : inventors.about.com Information : nobelprize.org Images : Google images Comics : ToonDoo
38. Thank You I hope you enjoyed my presentation
