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10.1 Light and the Electromagnetic Spectrum What to study: ● Colours ● Light ● Shadow ● Reflection ● Electromagnetic spectrum ● Wave model Nomenclature Aid Sheet The energy in a wave ● Wave is a disturbance that transfers energy from one point to another without transferring matter. Nomenclature Aid SheetNomenclature Aid SheetProperties of Waves ● The highest point of the wave is called a crest. ● The lowest point of the wave is called a trough. ● The level of the water when there are no waves is called the rest position. Three important properties of all waves ● Wavelength is the distance from one place in a wave to the next place of another wave. Nomenclature Nomenclature Aid SheetNomenclature Aid SheetSheetAmplitude is the height from the rest position of the wave to the crest or the wave depth from the rest position to the trough. ● Frequency is the rate of repetition of a wave (cycles/minute). Relationship between Frequency and Wavelength ● Creating more waves increase the frequency and shorten the wavelength. ● Inverse relationship. ● When one increases the other decreases. ● Formula to find speed is v (speed) = � (frequency) x �(wavelength). The Electromagnetic Spectrum ● Light is only a tiny fraction of the energy that surrounds us. ● Surrounded by invisible light-like waves. ● Invisible + visible light makes electromagnetic radiation.

● Electromagnetic radiation is a wave pattern made of electric and magnetic fields that can travel through empty space. ● The range is from shortening gamma rays to the longest radio waves and includes visible light. Called the electromagnetic spectrum.

Visible light Ultraviolet rays ● carry more energy than visible light and therefore have a shorter wavelength and higher frequency than visible light. ● Beneficial to the human body with certain amounts. ● Sources of rays are from the sun and other stars X-rays ● Are very high energy radiation that can penetrate human tissues. ● Used as a security measure to scan luggage at airports. ● Used to check for fractures or damage. Gamma rays ● Are extremely high energy radiation that can penetrate human tissues. ● Are used to sterilize medical equipment. ● Can use short bursts to kill a maximum number of cancerous cells and a minimum number of healthy cells. ● Produced from neutron stars and black holes. ● Whoever is dealing with gamma rays need to wear a shield such as a lead apron. The Wave Model of Light ● A model is a representation of an object, event, or a process based on our observations of its characteristics and properties. ● A property is an attribute common to all substances or objects of the same group. We use models to help us understand complex concepts. ● In the wave model of light, we use similarities between light and the movement of waves on the surface of the water to explain several properties of light we can use. ● A prism is a transparent glass or plastic object with flat, polished slides. ● The light separates into the colours of the rainbow. ● The range of different colours of light is called the visible spectrum.

● Additive Color Theory of Light ● The additive colour theory of light states that white light is composed of different colours (wavelengths) of lights. ● If you mix the right amount of the three primary colours, you will produce white light. ● Mixing two primary colours will produce a secondary colour. Subtractive Color Theory of Light ● When a light wave strikes an object some wavelengths reflect the light. ● They bounce off the object. ● Other wavelengths are absorbed. ● According to the subtractive colour theory of light, coloured matter selectively absorbs different colours of wavelengths of light. ● Absorbed colours are subtracted from the reflected light that is seen by the eye. ● ● Black objects absorb all colours. ● White Objects reflect all colours. ● Colours of light for the subtractive theory is opposite to the additive theory. ● Cyan, magenta and yellow are the primary subtractive colours. ● Red, green and blue are the secondary subtractive colours. ● Applies to pigments and colours that they absorb. ● A pigment is a powder used to colour substances.

10.2 Producing Visible Light Sources of Light ● Sun and starlight are called natural light. ● The light produced by human technology is called artificial light. Incandescent light ● Produced by an object (i.e. metal that is at very high temperature). Fluorescent Light ● The light emitted by some substance when they are exposed to electromagnetic radiation. Phosphorescent Light ● Ability to store the energy from a source of light and then emit it slowly over a long period. ● Glow in the dark toy. Chemiluminescence ● The light produced from a chemical reaction without a rise in temperature because the chemical gives off little heat. ● Sometimes called cool light. ● Like glow in the dark sticks. ● Also used in crime scenes. Detectives use a chemical called luminol to detect traces of blood because the chemical glows when reacts with iron found in the blood. Triboluminescence ● Producing light from friction. Electric Discharge ● Is a method for producing light in which an electric current passes through the air or another gas such as neon. ● Tube Lighting is an example. Light-Emitting Diode (LED) ● An electroluminescent light source made out of a material called a semiconductor. ● A semiconductor is a material that can be made to change how well it conducts electricity.

OLED ● A light source made of several extremely thin layers of organic molecules that use an electric current to produce light. ● Organic light-emitting display (OLED). Plasma Displays ● Can produce brighter images than an LCD display but requires much more electrical power to operate. ● Like when you turn on full brightness on a phone, it takes up more battery meaning more energy is taken up. Liquid Crystal Displays ● LCD. ● A solid that can change the orientation of its molecules like a liquid, but only when electricity is applied. ● Blocks light or transmit light depending on how much electricity is applied to it.

10.3 The Ray Model of Light Light and Matter ● Straight lines called rays which show the direction that light travels. ● Ray diagrams are drawings that show the path that light takes after it leaves its source. ● Helps explain why the brightness of light changes with distance. ● More rays of light, brighter the object appears. Transparent ● Materials such as clear glass or clear plastic. ● Absorbs and reflects very little light. ● You can see clearly through. Translucent ● Materials transmit some light, but not enough to see through the material clearly. ● A frosted window (a good example I think). ● Some light passes through but you cannot see what is on the other side in detail. Opaque ● Objects absorb and reflect light, but they do not transmit it. ● Can’t be seen through (solids) Shadows ● Occurs when an opaque object blocks the direct light from a light source. ● The umbra is the part of the shadow in which all light rays from the light source are blocked. ● The area of a partial shadow from a non-point light source is called the penumbra....