Cheatography

Waves - sound and light Cheat Sheet (DRAFT) by malak_mohamed

Year 9 I Lower Secondary *Qualification* Pearson|Edexcel

This is a draft cheat sheet. It is a work in progress and is not finished yet.

SOUND VIBRATIONS AND WAVES

 Sound is a way of transf­erring energy. Sounds are made when things vibrate.The vibrations are passed on by particles. Sound therefore need a medium (subst­ance) to pass on the vibrations ,so it can travel through solids, liquids & gases but not through empty spaces. The speed of sound is usually faster through materials in which particles are closer together. Closer particles hit each other more easily and so the energy is more likely to be passed from one particle to the next . Sound travels faster in solids than in liquids, and it travels slowest in gases

FREQUENCY AND AMPLITUDE

 The frequency of a sound wave is the number of complete waves passing a point each second. The unit of is the hertz(Hz). Pitch is how high or low a sound is. High frequency sounds have a high pitch. The amplitude of a wave is how far the particles move as the vibration pass. The larger the amplitude, the louder the sound .The loudness of a sound is also described as the volume or the intensity of the sound. The loudness of a sound is measured using a sound intensity meter . The units are decibels (dB)

ABSORBING, REFLECTING AND TRANSM­ITTING

Sound waves can be Reflected by a material. This usually happens if the material is hard. Soft materials Absorb some of the sound that reaches them, and Transmit only a little.

ABSORBING, REFLECTING AND TRANSM­ITTING (PT.2)

When a sound wave moves energy from one place to another, we say that the energy has been transf­erred. The energy spreads out in all directions unless something stops them. This means that the intensity of a sound gets less as you get further from its source

EARS AND HEARING

Sound is detected by ears and microp­hones. In a microphone, sound waves make a diaphragm vibrate, and electr­onics are used to convert the vibrations into changes in an electrical current.

EARS AND HEARING (PT.2)

The auditory range of an animal is the range of freque­ncies of the sound it can hear. Animals such as bats and dolphins can hear ultras­ounds (sounds with freque­ncies greater than 20 000 Hz). some animals can hear infras­ounds (frequ­encies less than 20 Hz)

USES OF SOUND

 Humans and other animals use sound for commun­ica­tion. Some animals [bats & dolphins], use ultrasound to locate their prey and avoid obstacles. Humans use ultrasound in sonar, to find the depth of the sea or locate fish or submar­ines. Humans use the energy transf­erred by ultrasound to clean delicate objects [Jewllery] or in physio­therapy (to relieve pain or aid healing)

COMPARING WAVES

 Transverse wave Waves on the surface of water. Particles vibrate at right angles to direction wave is travelling Longit­udinal waves Sound waves. Particles vibrate in same direction as wave travels All waves Transfer energy without transf­erring matter. can be reflected, transm­itted and absorbed. can affect other waves by **supr­tpo­sition , when their effect can add up or cancel out