Light and sound

• Electromagnetic wave


  consists of alternating electric and magnetic fields, have no mass and travel at the speed of light
• Rest


  The state of an object when it is not in motion
• Wavelength


  Distance between two crests (shorter wavelength carries more energy)
• Amplitude


  Height of a wave (higher the amplitude the taller the wave and carries more energy)
• Crest


  Highest point of a wave
• Trough


  Lowest point of a wave
• Frequency


  Counts the number of wavelengths that pass by a point in one second (measured in Hertz)
• A light's wavelength determines...


  Where it sits on the spectrum
• A shorter wavelength means

  higher frequency, higher energy
• A longer wavelength means

  lower frequency, lower energy
• Gamma rays


  Electromagnetic waves with the shortest wavelengths and highest frequencies
• X-rays


  electromagnetic waves with wavelengths shorter than ultraviolet rays, but longer than gamma rays
• Ultraviolet rays


  electromagnetic waves with wavelengths just shorter than those of visible light, can be felt as heat and causes skin cancer
• Visible light


  electromagnetic waves your eyes detect
• Infrared rays


  Electromagnetic waves with shorter wavelengths and higher frequencies than microwaves
• Microwaves


  Electromagnetic waves that have shorter wavelengths and higher frequencies than radio waves, used to detect speeding cars and heat food
• Radiowaves


  an electromagnetic wave that has the longest wavelength and has the least energy, used for communication
• Rod cells


  highly sensitive, function in dim light
• Cone cells


  see colour, function best in bright light
• Transparent


  Almost light is transmitted through, a clear image is shown
• Translucent


  Some light may be reflected and light that passes through is scattered, a fuzzy image is shown
• Opaque


  Light is reflected/absorbed and no light is transmitted, no image can be seen
• Luminosity


  the true brightness of an object
• Bioluminescence


  living organisms that can produce light
• Reflection


  Light bounces off an object and then into your eyes
• Regular reflection


  Reflection of light from a very smooth surface, produces a clear image
• Diffuse reflection


  Reflection of light in many directions from an uneven surface, no clear image is formed
• Law of Reflection


  The angle of incidence is equal to the angle of reflection
• Refractive index


  a measure of the light-bending ability of a medium
• Sound wave


  a longitudinal wave that is caused by vibrations and that travels through a medium
• Transverse waves


  particle vibration is at right angles to the direction the wave is travelling

  
• Longitudinal waves


  particle vibration is in the same direction as the wave is travelling

  
• Compression


  a region of high pressure, where particles are close together
• Rarefactions


  the regions of a longitudinal wave where the particles are farthest apart
• Pitch


  a tone's experienced highness or lowness, depends on frequency
• Volume (loudness)


  Amplitude controls the loudness of sound waves
• Light is a...


  Transverse wave
• Sound is a...


  Longitudinal wave
• Non-luminous objects are still visible because

  Light bounces off of them and into your eyes
• Unlike sound waves, light waves don't need a medium (solid, liquid, gas) in order to travel