Light is a type of energy. Light does not unless it encounters a different. In Albert Michelson in Mt. Wilson, California did an experiment:

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1 Properties of Visible Light Science 8 Light is a form of Light energy enables us to Light is a type of energy It is the form of energy that The lines in which light travels are called (the traveled by light) Light does not unless it encounters a different Determining the speed of light In Albert Michelson in Mt. Wilson, California did an experiment: He found the speed of light to be:

2 Visible light is a mixture of The colours we see are because the object we are looking at Example: An apple appears red because: Wave Model of Light This model describes light as a wave that travels through empty space and transfers energy from one place to another: Reflection of Light Light rays travel in lines and when they hit reflective surfaces they directions. We will study more on the reflection of light soon!

3 Refraction of light : Refraction is Each colour of light has a different characteristic (this is the ) Since each colour has a different wavelength, then each colour must also have a different A is a clear object that refracts light ( its direction) and the light into its ). Longer wavelengths are refracted than shorter wavelengths, and so the colours of the are separated by a Colours of the Rainbow Frequency Wavelength All of the colours that make up white light are collectively know as the When put all together, these colour of light make up light. Example Classroom lights, car lights do not seem to have a colour. These are classified as white lights.

4 Colour and Reflection : When light waves bounce off an object we call it If an object is black, that object If an object is red, then this means that objects absorbs except If an object is white, that object absorbs (It reflects ) The primary colours are The secondary colours are These colours OF LIGHT are created by mixing two of the additive primary colours: Blue + green = light Green + red = light Blue + red = light

5 Properties of Visible Light Science 8 Light is a form of energy Light energy enables us to see the world around us Light is a type of radiant energy It is the form of energy that we can see The lines in which light travels are called rays (the straight line paths traveled by light) Light does not bend unless it encounters a different medium

6 Determining the speed of light In 1926 Albert Michelson in Mt. Wilson, California did an experiment: Michelson accomplished this by using a Sperry arc lamp, one of the most powerful of the day. If the operators weren t careful, they d be burned by its ultraviolet emissions. The arc light was focused into a somewhat parallel beam by 24 diameter concave mirrors at each end of the link. Given the other necessary optics involved, aligning the system and keeping it that way was difficult. The actual measurement process was exceptionally clever. The primary measurement point, what Michelson called Mount San Antonio (today known as Lookout Mountain) was 22 miles away to the northeast. The light pulses sent from Mount Wilson to San Antonio were created by reflecting the arc light off a spinning, multifaceted mirror with either 8, 12 or 16 sides. The time it took a pulse of light to travel from Mount Wilson to Mount San Antonio and back to Mount Wilson (44 miles) was seconds. This happened to be the same amount of time it took a 16 faceted mirror, turning at 264 revolutions per second, to move one facet. When all was adjusted just so, the light pulse went out on one mirror facet and returned on the next one presenting what appeared to be a single image to the observer.

7 Determining the speed of light: MICHELSON-MORLEY EXPERIMENT He took two mirrors, 22 miles apart. These were rotating mirrors with 8 sides. Light was bounced back and forth between the mirrors and it was timed how long it took the light to bounce. He found the speed of light to be: 300,000 km/s Neil Degrasse Tyson Short demonstrative video More complicated / sophisticated explanation:

Visible light is a mixture of all colours of the rainbow The colours we see are because the object we are looking at reflects that colour back to our eye Example: An apple appears red because: The

8 Visible light is a mixture of all colours of the rainbow The colours we see are because the object we are looking at reflects that colour back to our eye Example: An apple appears red because: The apple reflects the red light and absorbs all the other colours Wave Model of Light This model describes light as a wave that travels through empty space and transfers energy from one place to another:

9 Reflection of Light Light rays travel in straight lines and when they hit reflective surfaces they change directions. We will study more on the reflection of light soon! Refraction of light : Refraction is the bending or changing direction of a wave as it travels from one material to another. Each colour of light has a different characteristic wavelength (this is the length of 1 cycle of wave) Since each colour has a different wavelength, then each colour must also have a different frequency A prism is a clear object that refracts light (changes its direction) and separates the light into its colours). Longer wavelengths are refracted less than shorter wavelengths, and so the colours of the rainbow are separated by a prism

10 Colours of the Rainbow RED ORANGE YELLOW Frequency GREEN Wavelength BLUE INDIGO VIOLET

11 All of the colours that make up white light are collectively know as the spectrum When put all together, these colour of light make up white light. Example Classroom lights, car lights do not seem to have a colour. These are classified as white lights.

12 Colour and Reflection : When light waves bounce off an object we call it reflection If an object is black, that object absorbs all colours If an object is red, then this means that objects absorbs all colours except RED! If an object is white, that object absorbs NO COLOURS! (It reflects all colours) The primary colours are RED GREEN BLUE The secondary colours are CYAN YELLOW MAGENTA

13 These colours OF LIGHT are created by mixing two of the additive primary colours: Blue + green = CYAN light Green + red = YELLOW light Blue + red = MAGENTA light

Red Orange the reflected ray. Yellow Green and the normal. Blue Indigo line. Colours of visible reflection

Red Orange the reflected ray. Yellow Green and the normal. Blue Indigo line. Colours of visible reflection distance the carrying the moves away from rest position Brightness Loudness The angle between the incident ray and the normal line Amplitude Amplitude of a light Amplitude of a sound incidence Angle between