Lecture 1 - Electromagnetic spectrum Flashcards
What is light
- Form of energy our eyes can detect
- Electromagnetic radiation/wave
What is an electromagnetic wave
Electric and magnetic components which oscillate perpendicular to its direction of propagation ( direction and motion of wave )
What are the two types of wave
- Transverse wave
- Longitudinal wave
What is a transverse wave
Vibrations right angle to direction of wave travel
what is a longitudinal wave
vibrations parallel to direction of wave travel
example of transverse wave
ripples in pond - water particles move up and down
example of longitudinal wave
sound - sound particles move back and forth
what is the electromagnetic spectrum
continuous range of radiation wavelengths
how do you get visible light
white light passes through prism - changes into spectrum of colours
what is a wave
the way in which energy is transferred between stores
vibrations/oscillations about a rest position
what is trough
lowest point
what is wavelength
distance between 2 peaks on same wave
what is amplitude
distance between centre of wave to peak
what is speed
the rate of travel of a wave in a certain direction
what is frequency
the number of complete waves generated per second
what is unpolarised light
both electric and magnetic fields vibrate in any randomly orientated plane perpendicular to direction of propagtion
no polarisation - electric fields oscillates in many different directions
how many directions does polarised wave oscillate
one
e.g. vertical only - horizontal blocked
which types of waves can polarisation happen for
transverse waves
how does polarized light work
molecules specially aligned that electric field only in ONE direction - 1 axis - vertical or horizontal
what happens with 2 polarizing filters parallel to each other
nothing - all light goes through- due to 2nd polarising filter
both same direction
what happens with 2 polarizing filters perpendicular to each other
nothing - no light gets through - due to 2nd polarising filter
uses of polarized light
- polarised sunglasses = reduces glare from reflecting surface - only lets through vertically polarised light
- polarisation of radio and microwave signals
- photo elastic stress analysis
