Understanding Sight Requires. Understanding Light Understanding the Eye-Brain

Size: px

Start display at page:

Download "Understanding Sight Requires. Understanding Light Understanding the Eye-Brain"

Valentine Gilbert
5 years ago
Views:

1 Seeing Things

2 Understanding Sight Requires Understanding Light Understanding the Eye-Brain

5 The Eye & Brain (- are part of how we see.)

6 Meet our Eye-Brain. We will use these often as observers on diagrams in this unit.

7 The tip of the candle flame emits light in all directions. But we only see the light that enters our Eye- Brain.

8 We don t see light that does not enter our eyes.

9 We don t see light directed away from our eyes unless it is reflected into our Eye-Brain by something.

10 On diagrams in this unit, we will tend to ignore all light that does not enter our Eye-Brains.

11 The path light takes is called a Ray. Diagrams that show how light moves from the object to the eye are called Ray Diagrams.

12 Light is a type of energy our eyes are sensitive to. This is called an Operational definition because it only tells us how we detect light but it does not tell us what light is.

13 Can you see the Eye-Brain s feet?

14 Light travels in straight lines. This is called Rectilinear Propagation. Since no ray of light can go straight from the Eye- Brain s feet into your eyes, you can t see them. Experience has trained our Eye-Brain to expect that things are located in the direction that the light comes from.

16 Newton was the first to note that white light breaks into the colours of a rainbow when it passes through a prism. These colours are called a Spectrum.

17 When light from the Sun (White Light) is broken down, it s Spectrum looks like this. White Light is made up of shades of Red, Orange, Yellow, Green, Blue, and Violet. A mnemonic for remembering the order of rainbow colours is the name Roy G Biv.

18 When light from some sources is broken down, it s Spectrum looks like a series of lines. All spectrum can be further separated until they appear as a series of lines. The above Line Spectrum is from light coming from an iron heated until it gives off light. Most light sources are made up of many different colours.

19 Newton noted that the individual coloured lines could not be separated further. These lines are pure colours and are identified by a frequency and wavelength number.

20 A Conceptual definition gives a better understanding of what light is. The atoms in sources that produce light are surrounded by electrons that can be excited to higher energy levels. As these electrons fall back to their original energy level, they give off the energy in the form of light.

21 There are many different ways for electrons to fall back. Each jump backdown produces a different coloured line of light. The Conceptual definition of light is; Light is produced when electrons change energy levels.

22 There are many ways for atoms to gain energy. For instance, Incandescence is the emission of light from a body due to its temperature. The atoms gain energy by being heated.

23 Our ears cannot hear some high sound frequencies that dogs can. Similarly, our eyes cannot see some of the colours of light.

24 For instance, you cannot see if an iron is hot or not. Our eyes are not sensitive to the colour the iron emits but our hands can feel it. The colour hot irons emit is called Infra Red Radiation. Some snakes can see Infra Red Radiation.

25 Similarly, you cannot see water heating in a microwave oven. Our eyes are not sensitive to the colour the water can absorb. The colour that water is heated by is called Microwave Radiation.

26 The Visible Light Spectrum is a very small part of a much larger spectrum called the Electromagnetic Spectrum.

27 Mnemonics for Remembering the Electromagnetic Spectrum from Long to Short Wavelength Radio Waves Microwaves Infra Red Visible Spectrum Ultra Violet X-Rays Gamma Rays Rabbits Mate In Very Unusual expensive Gardens My Favourite from Short to Long Wavelength Gamma Rays X-Rays Ultra Violet Visible Spectrum Infra Red Microwaves Radio Waves Girls/Guys experience Unusual Vibrations In My Room

28 Visible Light can be produced from many energy sources. Astronomical objects, Bioluminescences, Triboluminescence, Chemoluminescence, Fluorescence, Phosphorescence, Incandescent, Combustion, and Lightemitting diode are types of Luminous sources.

29 Atoms in Luminous Objects emit light rays in all directions produced from itself.

30 Atoms in Non-Luminous Objects scatter the light rays from Luminous Objects in all directions.

31 Atoms in all objects produce or scatter light rays. This diagram only shows light rays from atoms at the top and bottom of the objects.

32 To make diagrams simpler we only show one ray of light from the top and bottom of objects. Rays illuminating Non-Luminous objects are not shown.

33 To make things even simpler, we sometimes only show the rays coming from the top of the object. We always only show the light rays that enter the observer s eye.

34 Rays of light travel from the object to the observer s eye through a Medium. A Transparent Medium allows nearly all the rays to pass straight through unaltered. Air is a transparent medium.

35 An Opaque Medium absorbs or scatters all the rays. A text book is an opaque medium.

SNC2D PHYSICS 4/27/2013. LIGHT & GEOMETRIC OPTICS L What Is Light? (P ) What Is Light? What Is Light?

SNC2D PHYSICS 4/27/2013. LIGHT & GEOMETRIC OPTICS L What Is Light? (P ) What Is Light? What Is Light? SNC2D PHYSICS LIGHT & GEOMETRIC OPTICS L What Is Light? (P.380-391) What Is Light? For centuries, scientists have tried to understand the nature of light and its properties. Some of these properties are