# (b) Properties of waves

## 3.02 explain the difference between longitudinal and transverse waves

Transverse Waves:

• A wave that vibrates or oscillates at right angles (perpendicular) to the direction in which energy is transferred/ the wave is moving.
• g. Light

Longitudinal Waves:

• A wave that vibrates or oscillates at parallel to (along) the direction in which energy is transferred/ the wave is moving.
• g. Sound

## 3.03 know the definitions of amplitude, wavefront, frequency, wavelength and period of a wave

Key Definitions:

• Wavefront: Created by overlapping lots of different waves. A wavefront is where all the vibrations are in phase and the same distance from the source.
• Amplitude: The maximum displacement of particles from their equilibrium position.
• Wavelength: The distance between a particular point on one cycle of the wave and the same point on the next cycle.
• Frequency: The number of waves passing a particular point per second. Is measured in Hertz (Hz).
• Time Period: The time it takes for one complete wave to pass a particular point.

## 3.04 know that waves transfer energy and information without transferring matter

Waves can transfer energy and information with out transferring matter, for example sun light, it transfers energy as it makes the earth warm without bringing any matter.

## 3.07 use the above relationships in different contexts including sound waves and electromagnetic waves

You will need to use any of the in 3.05 and 3.06 to solve problems to do with sound waves and electromagnetic (light) waves

## 3.08 explain why there is a change in the observed frequency and wavelength of a wave when its source is moving relative to an observer, and that this is known as the Doppler effect

Doppler Effect:

• When a car is not moving and its horn sounds, the sound waves we receive are a series of evenly spaced wavefronts.
• If a car is moving, wavefronts of the sound are no longer evenly spaced.
• Ahead of the car wavefronts are compressed as the car is moving in the same direction as the wavefronts. This creates a shorter wavelength and a higher frequency.
• Behind the car wavefronts are more spread out as the car is moving away from the previous wavefronts. This creates a longer wavelength and a lower frequency.
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Section 1: Principles of chemistry

a) States of matter

b) Atoms

c) Atomic structure

d) Relative formula masses and molar volumes of gases

e) Chemical formulae and chemical equations

f) Ionic compounds

g) Covalent substances

h) Metallic crystals

i) Electrolysis

Section 2: Chemistry of the elements

a) The Periodic Table

b) Group 1 elements: lithium, sodium and potassium

c) Group 7 elements: chlorine, bromine and iodine

d) Oxygen and oxides

e) Hydrogen and water

f) Reactivity series

g) Tests for ions and gases

Section 3: Organic chemistry

a) Introduction

b) Alkanes

c) Alkenes

d) Ethanol

Section 4: Physical chemistry

a) Acids, alkalis and salts

b) Energetics

c) Rates of reaction

d) Equilibria

Section 5: Chemistry in industry

a) Extraction and uses of metals

b) Crude oil

c) Synthetic polymers

d) The industrial manufacture of chemicals

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