Waves

• transverse 


  oscillations are perpendicular to the direction of energy transfer
• examples of transverse


  electromagnetic waves
• longitudinal waves


  oscillations are parallel to the direction of energy transfer
• examples of longitudinal


  sound waves, shock waves
• em waves are made of oscillating electric and magnetic fields
• all objects continuously emit and absorb infrared
• the hotter the object the more infrared radiation is emitted
• period(s) = 1/frequency(Hz)
• waves transfer energy from one place to another without transferring any matter
• wave speed(m/s) = frequency(Hz) X wavelength(m)
• convex lens


  bulges outwards, causes rays of light parallel to the axis to be brought together (converge) at the principle focus
• concave lens


  caves inwards, causes rays parallel rays of light to spread out
• secular diffusion 


  when a wave is reflected in a single direction by a smooth surface
• diffuse reflection


  when a wave is reflected by a rough surface
• real image


  the light from an object comes together to form an image
• virtual image


  the rays are diverging so the light from the object appears to be coming from different places
• magnification = image height/object height
• colour filters


  filter out different wavelengths of light so only certain colours are absorbed
• echoes are reflected sound waves
• sound waves are created by vibrating objects that pass through the surrounding medium as a series of compressions and rarefaction, they travel fastest in solids