Let There Be LIGHT!

 Optics: is the study of the behaviour and properties of light  Light is a form of ENERGY  Visible light makes up only a small fraction of the Electromagnetic Spectrum  Light energy travels as a wave and its properties are dependant on its wavelength

 Recall that heat energy can be transferred by either conduction or convection. Conduction and convection both require a medium for transmission (solids, liquids and gases).  Medium: any physical substance that acts as a carrier for the transmission of energy.  Light energy is transferred through radiation and does not require a medium for transmission.  Visible light is one of many types of electromagnetic waves, and is the only type that the human eye can detect.  Scientists classify electromagnetic waves based on the energy of the waves in a classification system called the electromagnetic spectrum.

A. What colours did you see when the light from the ray box shone through the prism? B. What is the order of the colours?

 The additive colour theory of light states that white light is composed of different colours (wavelengths) of light. It is possible to produce white light by combining the three primary colours. If you mix only two of the primary colours, you will produce a secondary colour.  Primary additive colours: Red, Green, Blue (RBG)  Secondary additive colours: Cyan, Magenta, Yellow (CMY)

 When a light wave strikes an object, some wavelengths of light are reflected and others are absorbed. The colour you see when you look at an object depends on the wavelengths that are reflected.  Coloured matter selectively absorbs different wavelengths of light. Pigments are the powders used to colour substances. The colours that are absorbed by pigments are “subtracted” from the reflected light that is seen by the eye. Ex. A blue object reflects blue and absorbs all other colours. Black objects absorb all colours and reflect none (black body).  Primary and secondary colours of light for subtractive theory are opposite to the colours of additive theory.  Primary subtractive colours: Cyan, Magenta, Yellow  Secondary subtractive colours: Red, Green, Blue

 Light can be modeled and compared with water waves.  Both light and water waves can transfer energy, and they both travel outward in all directions from their source.  Each colour of light has a different wavelength and frequency ColourFrequency (Hz)Wavelength (nm) red4.3 x orange5.0 x yellow5.2 x green5.7 x blue6.4 x violet7.5 x

 Crest: The highest point in a wave  Trough: The lowest point in a wave  Rest Position: The level where there is no waves.  Wavelength (λ): the distance from one place in a wave to the next similar place on the wave; for example, the distance from a crest to a crest.

 Amplitude: is the wave height from the rest position of the wave to the crest or the wave depth from the rest position to the trough. The energy transferred by a wave depends on amplitude: large amplitude = more energy. Small amplitude = less energy.  Frequency (Hz): is the rate of repetition of a wave. If wave crests pass a given point 10 times in a minute, then the frequency of the wave is 10 cycles/minute. The energy transferred by a wave depends on the frequency as well as the amplitude: The higher the frequency, the more energy the wave passes along. Hz stands for cycles per second.  Frequency and wavelength have an inverse relationship; as one increases, the other decreases. They are connected by the relationship speed = frequency x wavelength (v = f λ) Note: v is constant as the speed of light!