Parkland Junior High School 2010-2011 Properties of Light Parkland Junior High School 2010-2011

What is Light? Simply stated, light is the form of energy you can see. This energy can be produced naturally by the sun or fire, or artificially by light-producing technologies, like batteries. Radiation is the wave like transfer of light from its source in all directions. Light is often called radiant energy. Light from the sun is formed by nuclear fusion.

What is Light? Light sources are luminous or illuminated. Luminous objects produce their own light and can be either artificial or natural. Illuminated objects do not produce light but are seen because they reflect light from another object. Our most important source of natural light is the sun. ----- incandescent ------- produced by nuclear fusion

Light Intensity The amount of energy a surface receives depends on the intensity of the light. The more intense the light, the more light can be absorbed.

Types of Light Incandescent light is light that is so hot it glows Examples: candles, fire, incandescent light bulbs etc Luminescent sources of light do not need to be hot to glow. Examples: fireflys, glow in the dark toys, fluorescent light bulbs

Sources of Light - Artificial Incandescent fluorescent phosphorescent chemiluminescent

Incandescent Light Dictionary.com Emitting light as a result of being heated. (of an electric light) Containing a filament that glows white-hot when heated by a current passed through it. Electrical energy →→Thermal energy →→ Visible light energy Regular household light bulbs

Fluorescent Light Ultraviolet light is absorbed by fabric particles, which in turn emit some of the energy as light – glowing Ultraviolet light energy→→ Energy absorbed by particles →→ Visible light energy This form of light does not give off heat. Light does not give off

Phosphorescent Light light energy is stored and released later as visible light For example, glow in the dark toys that glow after all light has been removed. First, let's distinguish phosphorescence from fluorescence. A fluorescent paint glows under a UV lamp, but stops glowing as soon as the lamp is turned off. A phosphorescent paint keeps glowing for a while.

Chemiluminescent Light light energy released by chemical reactions These chemical reactions produce light but not heat. http://www.youtube.com/watch?v=8CbE01hyjig Many chemical reactions produce both light and heat. A burning candle is such a reaction. When a candle is lit, its flame both glows and becomes hot. It is much less common for a chemical reaction to produce light without heat. The light from such reactions is called cool light, because it is created without heat. Reactions that produce light without heat are called chemiluminescent reactions. http://scifun.chem.wisc.edu/HomeExpts/Chemilum.html

Sources of Light - Natural

Bioluminescent Light Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". This type of light is a form of chemiluminescent light. http://ed.ted.com/lessons/the-brilliance-of-bioluminescence-leslie-kenna http://www.helium.com/items/2105414-best-bioluminescent-bays-in-the-world

First Property of Light The first basic property of light is that light is a form of energy. Energy radiates from the Sun in all directions. When light reaches a surface, it can be absorbed and transformed into other types of energy. This type of energy transfer does not require matter and is known as radiation.

When light reaches a surface, it can be absorbed and transformed into other types of energy… … into electrical energy Solar cells change light into electricity

Electric Pickle Lab - Shows that light is energy http://www.youtube.com/watch?v=QZieGLO9_ks

Cameras change light into thermal images When light reaches a surface, it can be absorbed and transformed into other types of energy… … into thermal energy Cameras change light into thermal images

Trees convert light energy into food (chemical energy) When light reaches a surface, it can be absorbed and transformed into other types of energy… … into chemical energy Trees convert light energy into food (chemical energy)

Transmit Sound using Light Demonstration - Show that light is energy, light travels in straight lines - Really neat demonstration - http://www.youtube.com/watch?v=mLo8h3tlyvo http://www.wikihow.com/Transmit-Audio-With-a-Laser-Pen

Second Property of Light The second basic property of light is that it travels in a straight line from its source. Until light strikes something, it will continue to travel in straight lines away from the source. The light will react in different ways depending on the substance it hits.

When light strikes…. When light hits clear substances such as air and water, it passes through them. These substances are transparent. A substance that lets some light pass but the light is scattered from it’s straight path is called translucent. A material that does not let any light pass through is called opaque.

Reflection occurs when light bounces off a surface.

Reflections Light sources are luminous or illuminated. Luminous objects produce their own light and can be either artificial or natural. Illuminated objects do not produce light but are seen because they reflect light from another object. Our most important source of natural light is the sun. ----- incandescent ------- produced by nuclear fusion

it is created by Mr. Parr who has some amazing science songs. http://www.youtube.com/watch?v=P_PVz8HrrCI&index=7&list=PL8123B2034AE0FCB3#aid=P7yKaY14e_A

The Color Spectrum

Properties of Light - recap 1. Light is a form of energy. 2. Light travels in a straight line. 3. Light can be separated into different colours.