Physical Science (Final Exam)

• kinds of electromagnetic spectrum:

  Radio

  Microwaves

  Infrared

  Visible light

  Ultraviolet

  X-ray

  Gamma ray
• Electromagnetic waves - transverse waves, travel at the speed of light, can be reflected, refracted and absorbed
• Both light waves and radio waves are examples of Electromagnetic waves
• Infrared waves - the radiated heat you feel from a stove or fire
• Ultraviolet waves - the radiation that causes sunburns
• Microwaves - the radiation that used to cook food in a microwave.
• Wavelength - determines the distance over which their amplitude changes
• Radio waves can have wavelengths as wide as your arms and even longer
• Visible light waves - have wavelengths as small as a thousandth of the width of human hair
• The Double Slit Experiment - a famous experiment dating back to 1801
• Thomas Young - he made the double slit experiment
• he then concluded that the pattern he saw is due to the wave-interference phenomenon
• Coherent sources - are maintaining a constant phase relationship (same wavelength and frequency)
• Incoherent sources - the sources do not maintain a constant phase relationship with each other over time
• Monochromatic light - the light of a single wavelength for interference to work
• Interference - is the combination of 2 or more electromagnetic waveforms to form a resultant wave
• when two waves come close to one another their effects add together and the result is a larger wave
• crests - or highest parts of the waves, lineup perfectly,then the crest of the combined wave will be the sum of the heights of the two original crests
• the troughs is the lowest part of the wave
• constructive interference - in which two waves of the same wavelength interact in such a way that they are aligned, leading to a new wave that is bigger than the original wave
• destructive interference - when two waves are not perfectly aligned, the combined wave will have crests that are shorter than the crests of either original wave and troughs that are shallower than either of the incoming waves 
• visible light - also known as white light
• visible light - consists of a collection of a component colors and are often observed as passes through a triangular prism  
• upon passage through the triangular prism the white light is separated into its component colors
• dispersion - the separation of visible light into its different colors
• component colors:

  red

  orange

  yellow

  green

  blue

  violet
• scattering of light - light rays get deviated from its straight path on striking and obstacle like dust or gas molecules water vapors etc.
• scattering of light gives rise to many spectacular phenomena such as Tyndall effect
• tyndall effect - is the phenomenon of scattering of light by colloidal particles.
• tyndall effect - is used to identify a true and a colloidal solution
• examples of tyndall effect:

  • beam of light is projected on a screen from a projector in the cinema hole.

  •beam of sunlight enters the dark room.

  •sunlight passes through the canopy of a dense forest
• Rayleigh scattering - refers to the scattering of light off of the molecules of the air and can be extended to a scattering from particles up to about a tent of the wavelength of the light
• rayleigh scattering - can be considered to be elastic scattering since the photons energies of the scattered photons is not changed
• Laser beams - are directional their intense and narrow only about 0.5 mm in diameter
• examples of laser beams:

  •cds are read by interpreting variations

  •barcode scanners

  •to cut steel and other metals