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Light - Coggle Diagram
Light
Light
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Mediums that allow light to pass through are called transparent. Some mediums scatter light after it passes through them. They are translucent. All other mediums don't let light through. These are opaque substances.
Light reflects off everything. Things which are very smooth reflect light straight back. This is called specular reflection and is found on water and on mirrors. When light hits a rough surface it reflects in other directions. This is called diffuse scattering
Colour
White light is a mixture of all of the colours of the rainbow (red, orange, yellow, green, blue, indigo, violet).
Violet has the most energy and is the highest frequency and red light has the least energy and lowest frequency
Object have certain colours because when white light is shone on them, they absorb all the colours except the colour they are. For example, a red apple would reflect red and absorb all the other colours.
If a red apple was exposed to blue light, it wouldn't reflect anything and would appear black, as it would have absorbed the blue light
Filters
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A magenta filter would only let blue and red through and a green filter would only let green through.
The primary colours are red, blue and green. Red + blue = magenta, blue+ green= cyan and red + green = yellow. These 3 are called secondary colours.
Refraction
When light hits a medium at an angle, it will refract depending on whether the medium is more or less dense then the medium it came from.
If light goes from a less dense medium to a more dense medium, it will slow down. If the light came in at an angle it would bend towards the normal
If light goes from a more dense medium to a less dense medium, it will speed up. If the light hit the medium at an angle, it would bend away from the normal.
When white light is shone through a prism, the violet light bends the most and the red light bends the least, creating a rainbow.
The Human Eye
The human eye has 6 main parts: the cornea, iris, pupil, lens, retina and optic nerve
The cornea is the outer transparent tissue protecting the eye. It refracts the light and roughly focuses it on the retina.
The pupil is a hole that allows light into the eye. It is controlled by the iris, a coloured ring of muscle that opens or closes the pupil based on how much light there is in the surroundings. If there is more light, the pupil will appear smaller and vice versa
The lens is behind the pupil. It focuses the light onto the retina. The image that falls on the retina however is upside down
The retina is at the back of the eye. It has lots of photoreceptive cells called cones and rods. Cones respond to colour and rods respond to tone and brightness.
The optic nerve is a nerve that connects the eye to the brain. It receives the signals from retina and sends them to the brain. The brain then flips the image and voila.
Solar Eclipses
When the moon comes in front of the earth and blocks the suns light, it creates a shadow. This is called a solar eclipse. They mainly happen out at sea. The shadowed area is called the umbra and the area in partial shadow is called the penumbra
When the earth comes in front of the moon, it casts the moon in shadow. This is called the blood moon. The moon looks red because as the light passes through the earth's atmosphere, it refracts and the red light falls on the moon.