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Light
Characteristics, velocity, frequency, wavelength, The Electromagnetic
Spectrum, Colors
Light
Significance of Light Responsible for photosynthesis Indirectly responsible for production of
Oxygen
tesCarbohydraOCOOH 222Sunlight
• Heats up ocean, air, and land which initiates different weather patterns
• Partly responsible for ocean currents• Partly responsible for evaporation and
condensation of rain.
Light is a Wave
Light is a wave because it displays some properties of mechanical waves.
It reflects. (Reflection) It diffracts. (Diffraction) It refracts. (Refraction.
Light as Electromagnetic Wave
• Light can propagate without the existence of physical medium (solid, liquid, gas)
• Light has velocity, wave length, and frequency.• Light is made up of “Many Light Waves”.
Invisible Light
Invisible Light
Gamma RaysX-RaysUltraviolet rays
Infrared raysMicrowavesRadio waves
High Frequency, short wave length
Low Frequency, Long wavelength
Electromagnetic Spectrum
Each light wave in the electromagnetic spectrum carries different Frequency and Wave Length, but their VELOCIY is the SAME.
300000km/s light) of v(speedfrequencyf
length wavevelocity
v
fv
Color
Visible Light (light with colors) – represent a band of light waves whose wavelength is between 380 nm – 739 nm.
Monochromatic light – a light wave of one wavelength
Colors – The light ray which is reflected.
White Light is the combination of all visible light.White – is not a color. Black – is also not a color. (No visible light is
reflected.Different organisms are sensitive to different wave
lengths.Snakes, and crocodiles – can see the red to infrared
color
Humans, and primates are sensitive to green colors
Bats – sensitive to infrared light
Human Eye
Retina – inside surface of the pupil. Collections of cells which are responsible for light detection.
Rods – Sensitive to the intensity of lightCones – Sensitive to the wavelengths of visible
light.
Cone Sensitivity Curve
Why are primates (humans, monkeys, apes) sensitive to green?
Colors – the color we see is the reflected light of ROYGBIV
Properties of Objects in Relation to LightTransparent – light passes straight through the
objectTranslucent – some light passes through, some
are reflected, some are refracted (scattered into many directions)
Opaque – no light passes through the object.
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