1. Introduction to Optics

2. 1. The Great Debate 2. What is light? 3. Properties of light 4. The wave-like model 5. Theories of colour

3.  A historical debate:

4.  Optics: is the study of the behaviour and properties of light

5.  Light: is a form of energy that travels in waves  Wave: is a disturbance that transfers energy from one point to another without transferring matter  We can use the properties of water waves to help us understand light waves (demonstration)  We use waves on the surface of water to explain properties of light that we can see  This is called a “model” a representation of an object, event or a process based on our observations of its characteristics and properties

6.  Crest: Highest point in a wave  Trough: Lowest point in a wave  Rest Position: Level of water when there is no waves  Wavelength: distance from one place in a wave to the next similar place on the wave. The symbol for wavelength is λ (lambda) and is measured in meters.  Amplitude: wave height from the rest position of the wave to the crest OR trough  Frequency: rate of repetition of a wave. The frequency is measured in hertz (Hz) which is cycles per second.

7. Label the diagram:

8.  Relationship between Frequency and Wavelength ν= f λ ν= the speed of light f= frequency f = 1/ λ λ = wavelength λ = 1/f  There is an inverse relationship between frequency and wavelength. When frequency increases, wavelength decreases, when wavelength increases, frequency decreases. How would energy relate?

9.  Light is a form of energy. Light travels in packets of energy called photons.  A photon is the smallest quantity of energy which can be transported.  Photons travel with wave-like properties Properties of Light  Light travels in straight lines (rectilinear propagation)  Light does not need a medium to travel, it travels in a vacuum - empty space with no matter  In vacuum or air, speed of light is constant (c = 3.0 x 10 8 m/s)

10.  Speed = distance/time or  If c = 3.0 x 10 8 m/s, then what is it in km/s? (300 000 km/s)  EXAMPLE #1 Calculate the time for light to travel from Toronto to Vancouver (d = 3400 km) c = 3.0 x 10 8 m/s  EXAMPLE #2 How long will it take for light to travel from the Moon to the Earth? (d = 400 000km) c = 3.0 x 10 8 m/s  Example #3 How long would it take a jet plane to travel this distance with the speed of 900 km/h, in days?

11.  The light that we see is called visible light, and is only a fraction of the energy that surrounds us  Electromagnetic radiation: wave pattern made of electrical and magnetic fields that can travel through empty space. The range is called electromagnetic spectrum

13.  It is called visible light because that is the only part of the spectrum which our eyes have evolved to detect.  The wavelengths of visible light range from 400- 700 (micrometer – 10 -6 of a meter)  Only objects within that size range will absorb and reflect light of that wavelength.  When light passes through a glass prism the light separates into the colours of the rainbow: Red Orange Yellow Green Blue Violet  This is called the visible spectrum

14.  Colours of the visible spectrum have different wavelengths:  Which colour has the longest λ, which has the shortest? ColourFrequency (Hz)Wavelength (nm) Red4.3 X10 14 700 Orange5.0 X10 14 600 Yellow5.2 X10 14 580 Green5.7 X10 14 550 Blue6.4 X10 14 450 Violet7.5 X 10 14 400

15.  Additive colour theory: white light is composed of different colours of light.  It is possible to produce white light by combining only three colours.  RED + GREEN + BLUE = primary colours = white light  2 primary colours = secondary colour (cyan, yellow, magenta)

16.  The subtractive colour theory of light: coloured matter selective absorbs different colours or wavelengths of light. The colours that are absorbed are subtracted from the reflected light that is seen by the eye.  A black object absorbs all colours, white objects reflect all colours.  Primary subtractive colours : cyan, magenta and yellow. Secondary subtractive colours are red, green, blue  a blue object reflects blue and absorbs all other colours  This theory applies to pigments and dyes

18.  An electron orbiting the nucleus of an atom receives sufficient energy to jump to a higher orbital shell. When it loses energy and falls back to the lower shell the energy it releases escapes in the form of a photon, or particle of light (and you see LIGHT)

19.  Incandescence: is the emission of light from a hot body due to its temperature. Ex. Light bulb (filament is heated to high temperature and glows)  Chemiluminescence: emission of light and heat as the result of a chemical reaction without a rise in temperature (called cool light). Ex. Glow sticks  Bioluminescence: ability for plant and animals to produce light. Occurs in marine animals.