Waves

Waves

1. Transverse Waves

   • The vibrations are perpendicular to the direction of energy transfer
   • Examples:
     • Electromagnetic waves
     • Ripples and waves on water
     • A wave on a string

2. Longitudinal Waves

   • The vibrations are parallel to the direction of energy tranfer
   • Examples:
     • Sound waves
     • Seismic and shock waves

3. Features

   • Amplitude is the height of the wave and measures the pitch
   • Wavelength is the distance between the same point on 2 different waves
   • Frequency is the number of complete waves in a second. Measured in Hertz
     • To work out frequency, it is frequency = 1/period(time)
   • Wave speed is the speed at which energy is transferred or the speed the wave is moving
     • Wave speed = Frequency x Wavelength

4. Reflection

   • Angle of incidence = Angle of reflection
   • Specular reflection happens when waves hit a smooth surface in a single direction
   • Diffuse reflection happens when the waves hit a rough surface and the waves are scattered in many directions

5. Refraction

   • It's when the wave crosses a boundary between materials and changes direction
   • Higher the density, slower the speed
   • The wavelength changes, the frequency doesn't
   • If the 2nd material is less dense, it goes away from the normal
   • If the 2nd material is more dense, it goes toward the normal

6. Lenses

   • Convex lenses bulge outwards and the light that goes through converges to the focal point
   • Concave lenses cave in and the light that goes through diverges away
     • Always produce virtual images
   • The principal focus is where all the light waves cross
   • A real image is where the waves come together to form an image
   • A virtual image is when the rays are diverging, the object appears to be somewhere else because of where the rays meet
   • Describe an image with the size, real or not and if it's upside down

7. Seismic waves

   • P-waves
     • Longitudinal
     • Can travel through solids and liquids
     • Faster than S-waves
   • S-waves
     • Transverse
     • Can travel through solids
     • Slower than P-waves
   • You can work out how the Earth is made up

8. Sound

   • Sound is made by vibrating objects
   • Longitudinal
   • Travels faster in solids than other mediums
   • Can't travel in a vacuum
   • Causes other particles to vibrate, passing along the sound
   • Ears
     • Go through and cause your ear drum to vibrate
       • This passes on to your ossicles then in to your cochlea
         • Which converts the vibrations into electrical signals and send the signal via the auditory nerve to the brain
     • Can only pick signals between 20 and 20,000 Hz
   • Reflected against hard surfaces
   • Refract in different mediums
   • Ultrasound
     • Used because of partial reflection
       • When a wave passes into a different medium, some is reflected, some is refracted
       • This can be used to check where boundaries are in places because some waves will be reflected when hitting a different medium

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