Waves
&
Sound
Sound is a crucial part of our survival. Being able to communicate through sound has allowed us to create languages and connect as a society, but what is sound?
Sound is caused by vibrations through a medium (solid, liquid or gas).
A sound wave is a vibration that transfers energy (or information) through a substance (water or air).
So what is a Wave?
A wave is an Oscillation or Vibration that transfers energy or information.
Both Light and Sound come in waves (Radio waves, gamma rays, visible light and sound waves). Waves can exist in 2 forms.
Transverse (Light) or Longitudinal (Sound)
All types of waves, although are different, share 3 important features.
- An Amplitude -
Distance between the middle to the top or bottom of the wave. - A Frequency -
Number of waves that go past per second. - A Wavelength -
The distance from one point on a wave to the same point on the next wave.
When it comes to light and sound, particles oscillate. This means they follow an up and down path as if on a roller coaster.
At the top of the roller coaster is the peak (crest) and at the bottom is the trough.
Notice how the particle Oscillates up and down in a wave.
The animation to the right shows different frequencies.
Notice as the frequency goes higher, the oscilations become more frequent and compact.
As opposed to a low frequency which is more spread out and less waves.
In Transverse waves the oscillation is at 90 degrees to the direction of the wave.
This creates the up, down motion seen to the left.
This is how waves of light travel
In transverse waves oscillation is up and down, and the flow of energy is in a single direction moving forward.
The easiest way to think about this is if you had a row of beads, and you flicked them. The beads would move up and down, while the wave move through.
In Longitudinal waves the oscillation is parallel to the direction of the wave.
This means, that unlike transverse waves, the particles move in the same direction (parallel) to the waves.
Observe the animation to the left. As the beads are pushed, the wave goes left to right and the motion of the beads also goes left to right. Unlike in transverse waves where the beads go up and down.
Similarly to transverse waves, longitudinal waves have different phases and points.
Compression -
Rarefaction -
How do you see your self in the mirror? The mirror isn’t emitting a light, your not emitting light, so how is it you are able to see your self in the reflection?
The reason is, that light bounces off you, onto the mirror and back into your eyes.
Waves can bounce of surfaces and barriers. This wave bouncing is called Reflection.
The light hitting the mirror is called an incident wave, while the light bouncing off back too your eyes is called a reflected wave.
When you echo, the sound waves coming out of your mouth are the incident waves, while the waves bouncing off the walls back to you are the reflected waves.
Questions
Don’t forget to write down the questions you got wrong in full!
Short Answer Questions
1. What is meant by the term Oscillation
2. Describe the difference between longitudinal waves and transverse waves
3. Give 3 examples of light energy
4. Draw a diagram of a transverse wave and label, Peak, Trough, Amplitude and wavelength
5. Draw a diagram of a transverse wave at High frequency and another one at Low frequency.
6. Explain how we see your reflection in shiny objects (use the following words: light, waves, reflection, Incident wave, Reflected wave, sun and surface).
