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.