Overview

Unit 1: Section C

Exam in January

Assignment B

Do it now!

What is a wave?

Name the different types of waves?

Give examples of each

Draw and label a wave diagram

What is the wave equation?

Waves in communication

L.O

Period

Frequency

Wavelength

Phase

Working with Waves

Oscillation

Frequency

Periodic time

Displacement

Amplitude (max displacement)

Investigating a pendulum

Complete the pendulum practical

Calculate the frequency of the waves at each pendulum length

What do you think happens to wave length?

What are the sources of error for thios investigation?

How did we limit them?

Why do we do repeats?

**BTEC: Waves and Communication**

Do it now!

Name the two typ of wave

Describe the differences between the two types of wave

What is amplitude?

What is the period of a wave?

what is the frequency of a wave?

Draw a wave diagram for a pendulum and label the stages

Wave equation

Speed= wavelength / Periodic time

easier to use frequency as periods are often very small fractions of time

Speed= frequency X Wavelength

In Phase

Graphical representation of wave features

Crank shaft and circular motion

one complete oscillation of a piston = one complete turn of the crank shaft

same periodic time and frequency

Graphs are typically sine waves for circular motion.

Phase

Phase= same point same thing

Out of phase not the same point or thing

Phase difference= difference in phase angle between two waves of the same frequency and wavelength

360 degrees or 2 pi raans represents a single whole cycle of wave form

Radans

Degrees measure angles by how far we tilted our heads. Radians measure angles by distance traveled.

But absolute distance isn’t that useful, since going 10 miles is a different number of laps depending on the track. So we divide by radius to get a normalized angle:

A circle has 360 degrees or 2pi radians — going all the way around is 2 * pi * r / r. So a radian is about 360 /(2 * pi) or 57.3 degrees.

Now don’t be like me, memorizing this thinking “Great, another unit. 57.3 degrees is so weird.” Because it is weird when you’re still thinking about you!

Moving 1 radian (unit) is a perfectly normal distance to travel. Put another way, our idea of a “clean, 90 degree angle” means the mover goes a very unclean pi/2 units. Think about it — “Hey Bill, can you run 90 degrees for me? What’s that? Oh, yeah, that’d be pi/2 miles from your point of view.” The strangeness goes both ways.

Radians are the empathetic way to do math — a shift from away from head tilting and towards the mover’s perspective.

What’s In A Name?

Radians are a count of distance in terms of “radius units”, and I think of “radian” as shorthand for that concept.

Strictly speaking, radians are just a number like 1.5 or 73, and don’t have any units (in the calculation “radians = distance traveled / radius”, we see length is divided by length, so any units would cancel).

But practically speaking, we’re not math robots, and it helps to think of radians as “distance” traveled on a unit circle.

Waves and Communication

L.O

Graphically representing waves

Polarising of Electromagnetic waves

Do it now

What is wavelength?

What is phase difference?

What is the frequency of a wave?

What is amplitude?

What is the frequency of a wave if it has a speed of 300,000,000 m/s and a wavelength of 1m?

Figure 1.43

use this graph to draw out the graph for a rotating vector.

label the phase angles in dergrees and radians

Figure 1.44 and 1.46

cut out these graphs and stick them in your notes

explain what they show

Diffraction

Polarisation of light

how expensive sunglasses work

can be done to aall electromagnetic waves

only allow light from one plane

removes glare from reflected surfaces