Radioactivity

• Waves


  Transfer energy without transferring matter
• Waves


  • Water waves at the beach
  • Electromagnetic waves
• Wave


  • Crests (tall bits)
  • Troughs (low bits)
  • Amplitude (height from rest position)
  • Wavelength (distance between crests)
• Frequency

  Number of wavelengths that pass a point per second
• Calculating frequency


  Divide velocity by wavelength
• Units


  • Frequency (Hertz)
  • Wavelength (meters)
  • Velocity (meters per second)
• Types of waves

  • Transverse (vibrations up and down)
  • Longitudinal (vibrations left and right)
• Transverse waves

  • Light waves
  • Water waves
  • Waves on the electromagnetic spectrum
• Longitudinal waves


  • Sound waves
  • P-waves (seismic)
• Sound wave pitch


  • High pitch = short wavelength
  • Low pitch = long wavelength
• What can happen when a wave hits a new material

  1. Transmitted

  2. Absorbed

  3. Reflected
• Refraction

  Change in direction of a wave when it passes from one medium to another
• Refraction


  1. One side of the wave hits the new material first, slowing down and changing speed first

  2. Other side still travels at normal speed, pulling the wave round
• Angle of incidence


  Angle the wave enters the new material
• Angle of refraction


  Angle the wave changes direction by
• Reflection


  Wave bounces back off a surface
• Angle of incidence


  Equals angle of reflection
• Types of reflection


  • Specular (flat surface, uniform reflection)
  • Diffuse (rough surface, scattered reflection)
• Uses of reflection


  • Ultrasound (high pitched sound waves reflected back)
• Electromagnetic spectrum


  Range of all transverse waves depending on frequency
• Visible light


  • Small part of the electromagnetic spectrum
  • Only part human senses can detect
• White light


  Made up of all colors on the spectrum
• Object color


  Reflects the color we see, absorbs other colors
• Black objects


  Absorb all light
• Transparent/translucent objects


  Allow light to pass through
• Lenses


  • Convergent (bring light to a focus)
  • Divergent (spread light out)
• Convergent lenses work like the lens in the eye, bringing light to a focus