Unit P3 – Waves Lesson 01 – Reflection and Refraction Aims: Understand that light is reflected from a mirror in a predictable way Understand the laws of reflection and refraction Questions… 1.Describe a situation that proves light travels faster than sound 2.What happens to light when it hits a mirror? 3-Nov-15

Amplitude… The height of a wave is known as the AMPLITUDE… Amplitude

Wavelength The distance between two waves is known as the WAVELENGTH…

The number of waves hitting the beach each second is known as the Frequency

Speed of Waves… You are standing on the beach… The wavelength is 3m (there are 3 meters between each wave) 2 waves hit your feet each second (yes… they are fast waves!) Distance of water passing your feet each second… = 3m (length between each wave) x 2 (waves per second) = 6m Speed of wave= wavelength x frequency = 3mx 2 Hz= 6m/s

Beach…

3 waves pass Ernie’s feet, each second In one second 3 waves pass Ernie’s feet 2m Frequency………. Wavelength……… Distance of wave…… Speed of wave………

1.Copy the diagram of the wave… Label the wavelength and amplitude. 2.Copy and complete this table that compares longitudinal and transverse waves… 3.Are water waves, longitudinal or transverse, draw a diagram to explain. 4.Explain what refraction is. FeatureTransverse WaveLongitudinal Wave These waves transfer energy Regular disturbances can be seen Disturbances move from side to side Disturbances move forward and back

White light Is a mixture of…RedRichard Orangeof YellowYork GreenGained BlueBattles Indigoin Violetvain A prism will split white light up into the seven colours Raindrops will also split up light, we see a rainbow if the weather is sunny and rainy.

Things to do… AQA Text book, page Copy diagram of electromagnetic spectrum. Use two pages and give an example/diagram and use of each type of electromagnetic radiation. E.g. X -Rays Taking pictures of bones

Echo-Location Ships use SONAR Question… Speed of sound in water = 1500 m/s An echo takes 4 seconds to bounce off the sea, bed how deep is the sea? Answer… Distance = speed x time = 1500 m/s x 3s = 6000 m But this is the total distance, the sound wave travels. [to the sea bed and back]. Depth = 6000m ÷ 2 = 3000m

Analogue and Digital Analogue Normal sounds A constantly changing signal. Easy to receive and interpret Signal quality gets lower over long distance Digital Information on a CD A series of zero’s and one’s (on / off) Signal must be converted into 1’s and 0’s, and then back again Data is tranferred easily as even if quality of signal degrades it is easy to tell if the signal is on (1) or off (0)

Converting from Analogue to Digital

Time / s Voltage / V Analogue > Digital Analogue wave

Time / s Voltage / V Analogue > Digital Fit digital signal over wave

Time / s Voltage / V Analogue > Digital Voltage conversion…

Time / s Voltage / V Analogue > Digital Digitise signal…

Raw Data  Maximum value = 50, so send data in chunks of 50 numbers… 7= = = Etc… The data is sent as a series of 1’s and 0’s (on /off), but first a message must be sent to inform the receiver to accept data in chunks of 50 At the receiver the data is converted back into a signal of baring voltage…

At the Reciever… First a message is received telling the receiver to accept data in chunks of 50… = = =28 Then the data is put together…

Time / s Voltage / V Digital > Analogue Put the wave back together…

Time / s Voltage / V Digital > Analogue Wave…

Time / s Voltage / V Digital > Analogue Wave… Original analogue signal

Time / s Voltage / V Digital > Analogue Wave… The new signal is not an exact copy, but quite close – more samples would make it better quality….

1.Speech is an analogue form of communication. Giving someone a ‘Thumbs-up’ is digital. Describe some other forms of digital communication. 2.Give two advantages of transmitting television signals via digital fibre optic, rather than analogue waves. 3.The diagram shows a bar-code. It is a series of thick and thin black stripes. Is that an analogue or digital signal – explain your answer. 4.The diagram shows an analogue sound wave. Copy the diagram, but add a digital signal that would sound the same. 5.Compact discs store music digitally. There are samples each second. New (super audio) CD discs have samples each second. Explain how this will reproduce the sound wave more accurately.