The Challenge of Light

Size: px

Start display at page:

Download "The Challenge of Light"

Kerry Bryan
5 years ago
Views:

2 Thomas Alva Edison

3 The Challenge of Light We have been studying light for years Do we know everything about it? Absolutely not! Greeks & Chinese have been using light for years with no real concept of how to use it or how it worked proof? Archimedes!

4 Archimedes A Greek scientist Believed you could use light from the sun and, using a lot mirrors, reflect that light to Burn enemy ships Do you think it worked?

5 Archimedes Absolutely, 100%, not even one bit at all! Why do you think it did not work? MythBusters

6 The Early Years Many people want to study and understand light One of the 1 st theorists was Pythagoras His theory Light was made of beams Beams came from a person s eyes in straight lines Sight occurred when these beams touched an object

7 The Early Years

8 The Early Years What is the major flaw we can see with this theory? If that is how light worked we could see in the dark! Who else guessed? Euclid He discovered when light hits a flat mirror that the reflected light is the same angle coming off

9 The Early Years Same angle Same angle

10 The Early Years About 1000 AD Plotemy described how light bends when travelling from air to glass During roughly this same time period we meet Arab scientist al-haytham What did he do?

11 The Early Years He accurately described how light bounces off objects and then travels to the eye! Essentially that light travels to the eye and not from it well done! He also studied other properties of light like how rainbows work Rainbow 1 but did not have Humans 0 much luck!

12 The Early Years Next in line was Sir Isaac Newton He loved rainbow - specifically their colours and wondered Performed some experiments with prisms! Where does coloured light come from? #Huh? What did he discover?

13 The Early Years

14 The Early Years Now we know beams of light travel to the eyes but how fast? The first solid finding came from Ole Romer in 1676 but during the 1920s Albert A Michelson measured it accurately! How did he do this?

15 The Early Years Measured Distance 34.5 KM Measured the time it took to reach the other mountain and divided the distance by time Light travels km/s in earth s atmosphere!

16 So what do we know? We know these basic properties Light travels in straight lines Light can be reflected Light can bend Light is a form of energy What a good test question this could be

17 Optical Devices So what is optical device? Any technology that uses light simple (mirror) to complex (telescope)

Optical Devices - Microscope First microscope

Hans & Zacharias Jansen First major discoveries

in the 17 th century He was among first to see

18 Optical Devices - Microscope First microscope believed to be built in 1595 in the Netherlands by Hans & Zacharias Jansen First major discoveries with microscopes came from Antoine van Leeuwenhoek in the 17 th century He was among first to see bacteria, algae & red blood cells Called them little animalcules

19 Optical Devices - Microscope His discoveries led to a whole new branch of science known as microbiology! So how do microscopes work? They use at least two lenses (eyepiece & objective lens) Light shines through the specimen and passes through the objective lens which produces a large image and focuses it onto the eyepiece lens which flips the image so you can see it!

in the 17 th century in the Netherlands!

20 Optical Devices - Telescope Take They that! No invented one out invents what?! me! The key tool to astronomers people who study stars and planets Again, 1 st one came in the 17 th century in the Netherlands! News of this travelled really quickly to Italian scientist Galileo This got him pretty fired up and he invented his own in 1 day!

21 Optical Devices - Telescope So what was the big deal with Galileo? He discovered craters and mountains on the moon Saw small objects orbiting Jupiter Saw Venus has phases just like the moon So how is a telescope different than a microscope Not only does it magnify images but it collects light!

$Refracting Two lenses, one on each end of a long tube They gather light and$ focus it towards the eye piece Reflecting Large circular mirror curves

22 Optical Devices - Telescope So we know there are 2 types of telescopes Refracting Two lenses, one on each end of a long tube They gather light and focus it towards the eye piece Reflecting Large circular mirror curves inwards Gathers light extremely well Another mirror directs the light to the eyepiece

$They are essentially two short refracting$

23 Optical Devices - Binoculars Ah the wonderful world of observing nature! To do this we use binoculars How do they work? They are essentially two short refracting telescopes fixed together

25 Light Rays & Materials First things first light reflects! Ever been window shopping or reading a glossy magazine when suddenly you cannot see what you are looking at Chalk that one up to glare (light reflected from glass or glossy surfaces)

26 Light Rays & Materials Science uses ray diagrams to show how light travels These diagrams help explain why the brightness (intensity) of light changes depending on distance from the eye! Here is an example

27 Light Rays & Materials Owww! Sorry bro I think I figured this out!! #Yolo!

28 Light Rays & Materials Yup #Swag That s better right?!

29 Light Rays & Materials Shadows: Light hits object, cannot go further. Object between the light and our eyes the lack of light is a shadow!

30 Light Rays & Materials So knowing that about light what about different materials? Transparent: allows light to pass through so an object on the other side can be seen clearly!

31 Light Rays & Materials Translucent: allows some light to pass through but not all of it

32 Light Rays & Materials Opaque: These materials do not allow any light to pass through them at all. Shadows are created behind them.

33 Light Rays & Materials Look at your text book. It is visible, we can see it but how? Why? Luminous vs. Non-luminous! Non-Luminous: Does not produce light Luminous: Produces light So what though?

34 Light Rays & Materials Light from luminous sources hits (bounces off, reflects) other objects (like your textbook) and this reflected light is how we see everything around us. Need proof? Try to see when the lights are off. Light bulbs are luminous and without them on there is no light to bounce and see!

35 Light & Reflection There are two types of reflection Regular Reflection: light rays Same hit anglea smooth surface and reflect back 45 the same as they hit. o 45 o Same angle The image is perfectly clear as if it did not reflect at all

36 Light Rays & Materials Diffuse Reflection: Light rays strike an uneven surface and each individual light ray comes off at a different angle

37 Law of Reflection Rays that are incoming are known as incident rays Quite simply the shiner and smoother a surface the better the reflection the incident rays produce Plane mirrors (flat mirrors) provide the clearest reflection

38 Law of Reflection Angle of Incidence Normal Angle of Reflection 45 o 45 o Law of Reflection states that the angle of reflection is equal to the angle incidence.

39 Light & Curved Mirrors Convex Mirrors A mirror that is curved outward The opposite of a concave mirror in that light spread out rather than collected It creates the illusion that the object is coming from a small point behind the mirror Where do you see a convex mirror daily?

40 Light & Curved Mirrors Concave Mirrors Surface curves inward like a bowl When light hits the mirror the rays travel back to slightly different positions They eventually all intersect at a common point This is known as the focal point They are good at collecting light too!

41 Light & Curved Mirrors Focal Point

42 Light & Curved Mirrors Concave Mirrors The image formed depends on how far the object is from the focal point of the mirror If the image is far away the reflected image appears upside down The closer the image the larger it becomes If the object is between the focal point and the mirror it is enlarged and upright

43 Light & Curved Mirrors Focal Point

44 Light & Curved Mirrors Time to play with spoons!!

45 Light & Transparent Subs Light behaves like every other matter we know. If it passes through a different medium, air vs. water for example, Which glasses it are real? will behave differently.

$Light & Curved Mirrors So what causes this bend of the light? Refraction!$ particles in the way, so it travels smoothly In water, lots in the way so it

46 Light & Curved Mirrors So what causes this bend of the light? Refraction! Due to the change of speed of light In space it is a vacuum, in that there are no particles in the way, so it travels smoothly In water, lots in the way so it travels slower The more dense the object the slower the light and more intense the refraction

47 Light & Curved Lenses Convex & Concave Lenses First, a lens is a transparent material, usually glass, that passes light through it Concave Convex - Thin edges, thick centre - Thick edges, thin centre

Hubble Space Telescope

Hubble Space Telescope Before the first telescopes were invented at the beginning of the 17th century, people looked up at the stars with their naked eyes. The first refracting telescope that Galileo developed in 1609 was likely