Properties of Light Waves, particles and EM spectrum Interaction with matter Absorption Reflection, refraction and scattering Diffraction and polarization

EM Wave

Light waves Complex light Single wave = monochromatic light Coherent light = laser Polarized light

Electromagnetic spectra High frequency EM acts like a particle Low frequency EM acts like a wave

Interaction with matter Color occurs when molecules selectively absorb light of specific wavelengths High energy, short wavelengths, disrupts chemical bonds Infrared radiation affects bond vibrations and is perceived as heat (snakes, vampire bats have heat sensors, but poor resolution) Light is selective absorbed and reradiated in a transparent medium

Requirements for Vision Reflection off solid objects –Higher and lower frequencies pass through Straight-line transmission without scatter –Permits formation of spatial maps Refraction at the boundary of two media with different densities –Permits focusing and image formation by an eye behind a lens

Absorption depends on wavelength

Absorption depends on frequency

Water absorbs red faster than blue

Speed of light depends on media Speed of light is slower in water than in air (opposite to sound)

Light reflects and refracts air water Snell’s law = n 1 sin  1 = n 2 sin  2 where n i = refractive index

Refraction

Reflectance Diffuse (dull, matte)Specular (shiny)

Large angle causes internal reflections air water cell

Scatter depends on wavelength

Sun is yellow, sky is blue

Polarized Light

Polarized light indicates solar position

Refraction depends on frequency

Lenses focus light

Mammalian Eye

Far and near sightedness

Light Diffraction

Color

Color Spectra

Color has 3 dimensions

Light interference