Units 12, 13, 14, and 15: Sound, Light, and waves

There are two types of waves: Transverse and Longitudinal.

Sound waves

are longitudinal waves

are caused by vibrations in a medium

consist of compressions and rarefactions

need a medium to travel through (cannot travel through a vacuum)

between 330 and 350m/s in air

1500m/s in liquid

3000-5000m/s in solids

greater the amplitude, louder the sound

greater the frequency, higher the pitch

humans can hear between 20Hz to 20,000Hz

Ultrasound (higher than 20,000 Hz) is used in medical scans and depth calculations

Infrasound(lower than 20) is used by elephants and whales to communicate

Ok, I'm gonna be real here. reflection, refraction, lenses, images, and all that stuff are my least favourite parts. I'm gonna re-direct you to my good friend here who can explain this better than I can: https://www.savemyexams.com/igcse/physics/cie/23/revision-notes/3-waves/3-2-light/3-2-1-reflection-of-light/

Read from 3.2.1 to 3.2.9.

Here are some properties of waves:

Waves transfer energy without transferring matter

Wave speed (m/s) = frequency (hz) * wavelength (m)

frequency = 1/period

waves diffract when they pass through a gap or around an obstacle

Diffraction is greatest when the width of the gap = wavelength

waves do not diffract when gap is smaller than wavelength

Now, onto the electromagnetic spectrum, which are all transverse waves.

and their uses:

They all travel at the speed of light: which is 3*10^8 m/s.

high frequency/high energy EM waves such as x-rays and gamma rays can be dangerous (can damage cells and cause mutations)

Waves are converted to binary by an analogue to digital converter.

Digital signals transmit data more accurately and faster.

That's it for now. It is important to note that I have omitted certain details to make this as concise and helpful as possible. If there is something I have not covered here, please leave a comment on the forums.