Waves

What do waves do?

Waves transfer energy from one place to another without transfering matter (stuff)

What does a wave look like?

Amplitude- Maximum displacement of a point on a waves from its undisturbed position.

Wavelength- The distance between a point on a wave and the same point on an adjacent wave.

Frequency- The number of waves passing a point in a second (Hz (Hertz))

Wavespeed- The speed at which energy is being transferred

You can work out the wavespeed, frequency or wavelength by using the wave equation wavespeed = frequency x wavelength 

What's the relationship between the three?

The wavelength will be shorter if there is a high frequency and the wavespeed would be faster.

How do I find the time period of a wave?

You can find it from the frequency of a wave using the equation time period (seconds)= 1 / frequency

Waves are classified by mechanical or electromagnetic waves.

Mechanical waves- Vibrations that travel through a medium

Electromagnetic Waves- Travel at the speed of light through a vaccum

Examples of Mechanical waves:

• sound
• Water waves
• Seismic P-waves

Examples of Electromagnetic waves:

• Radiowaves
• x-rays
• Microwaves

All waves are either transverse or longitudinal. All electromagnetic waves are transverse but mechanical waves can be transverse or longitudinal.

Examples Mechanical waves that are longitudinal are sound waves and seismic p-waves.

Transverse Wave- Vibrations is right angles to direction of energy transfer (wiggles like a catapillar)

Longitudinal Wave- Vibration is parallel to the direction of energy transfer (like a spring)

Normal- A line at 90 degrees to the boundary in the centre

Angle of incidence- The angle between the normal and the incident ray of light

Angle of relection- The angle between the normal and the reflected ray.

Laws- The angle of incidence and relection are equal for a plane mirror. 

The image in a plane mirror is upright, laterally inverted, virtual and the same distance behind the mirror as the object is infront.

• Sound travels through solids causing vibrations in the solid.
• The human ear can detect a range of frequencies from 20hz to 20,000hz
• Sound is a mechanical wave that requires a medium to travel through and so cannot pass through a vaccum
• Humans can hear only a limited range of frequencies is because the conversion of soundwaves -the ear drum creating vibrations causing other parts to vibrate- to vibrations of solids can only work in limited frequency range.

Ultrasound can be useful for detection and exploration of structures/objects that cannot be seen by the eye. Ultrasound cannot be heard by humans because the frequency is higher than our range can detect. 

Ultasound can create echoes that detect objects in deep water or to measure the depth of the water.

The formula for measuring the depth of the water is Depth= 0.5 x wavespeed x time for echo to return

Ultrasound can be used for medical and industrial imaging.

Seismic Waves are produced by earthquakes, there are three types of seismic waves: p-waves, s-waves and l-waves.

P-waves:

• Longitudinal
• They travel through solids and liquids
• They are the fastest of seismic waves

S-waves:

• Transverse
• They can only travel through solids (not liquids or gases)
• They are slower than P-waves

L-waves:

• Are the slowest of seismic waves
• They create violent movements in the Earth's crust (the surface moves  up, down and side to side)

How do seismic waves produce evidence for the structure and size of the Earth's core?

• Because of where waves are absorbed or refracted.