Science-Waves

• What are the two types of waves?

  transverse and longitudinal
• What do waves transfer?

  Information and energy
• What are some examples of transverse waves?

  Light waves, radio waves, seismic S-waves, and water waves.
• What type of vibrations do transverse waves have?

  In transverse waves, the vibrations are perpendicular to the direction of energy transfer.
• What are some examples of longitudinal waves?

  Sound waves, seismic waves, and ocean waves are examples of longitudinal waves.
• What type of vibrations do longitudinal waves have?

  In longitudinal waves, the vibrations are parallel to the direction of energy transfer.
• What type of wave is shown in the picture below?

  A transverse wave

  
• What type of wave is shown in the picture below?

  A longitudinal wave

  
• In a longitudinal wave, the areas where particles are close together are called compressions, and the areas where particles are further apart are called rarefactions.

  The material that a wave travels through is called the medium.

  The speed of a wave depends on the type of wave, as well as the medium it is travelling through.
• How many metres does sound travel in one second in water?

  1400m
• Look at the diagram below. Which wave effect is being shown?

  Diffraction

  
• Do electromagnetic waves transfer energy?

  Yes
• What is an amplitude?

  The maximum displacement or distance from the equilibrium position in a wave.
• What is the frequency of waves?

  Hertz
• Sound waves are made by the particles in a medium vibrating.
• Match the words to the letters

  Compression: D

  Rarefraction: A

  Direction of energy: B

  Vibration of particles: C

  A) A

  B) B

  C) C

  D) D

  
• True or false?

  • Can travel through solids, liquids, and gases, because they are made of particles.
• • Cannot travel through a vacuum, because there are no particles in a vacuum.
• Sound can travel fastest through solids, because the particles are closest together.

   travel slowest through gases, because the particles are furthest apart.

  When waves travel through a material (medium), it is called transmission.

  Humans can hear sound waves with a range of frequencies.
• The frequency of a wave is the number of vibrations that happen each second. It is measured in hertz (Hz).

  The average human hearing range is between 20 Hz and 20,000 Hz.

  Sound that has a frequency above the human hearing range is called ultrasound.
• The pitch of a sound wave depends on the frequency.

  The higher the frequency, the higher the pitch. 
• The volume of a sound wave depends on the amplitude.

  The larger the amplitude, the louder the sound.

  The smaller the amplitude, the quieter the sound.
• Sound waves, like all waves, can be reflected.

  Reflections of sound waves are called echoes.
• Bats produce high-pitched sounds that reflect off obstacles and food (such as insects).
• Bats listen for the return of the sound wave (the echo) to work out how far away things are.

  The longer the sound wave takes to return, the further away the object is.

  This is called echolocation.

  Dolphins and whales also use echolocation to find food underwater.

  Submarines and self-driving cars use echolocation too, but in these situations it is called sonar.
• Although sound transmits through solids, liquids, and gases, some of the sound wave is absorbed.
• The further you stand from a person making a sound, the quieter they appear to be. This is because some of the wave is absorbed as it travels through a medium.
• When the sound wave is absorbed, energy is transferred to the material.

  The absorption of sound waves is used in designing sound-proofing materials for uses such as ear defenders and soundproof music studios.
• A submarine sends out a pulse of ultrasound to check how close it is to the sea bed. The reflected waves are detected 0.2 seconds later. Work out the distance from the submarine to the sea bed. The speed of ultrasound in water is 1500m/s.


  150m