P1.5- Waves

the nature of the nature of waves

measuring waves

reflection, diffreaction, refraction

sound

musical sound

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• Created by: gee
• Created on: 01-05-12 21:21

The Nature Of Waves (P1.5.1)

• Waves can transfer information and energy

Transverse

• vibrations travel at right angles to the direction of energy transfer
• all electromagnetic waves

Longitudinal

• vibrations travel parrellel to the direction of energy transfer
• sound waves (and others)
• rarefractions and compressions

mechanical = need a medium (substance)

electromagnetic = do not need a medium (substance)

= can travel through a vacuum

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Measuring Waves (P1.5.2)

amplitude = the distance from the middle (resting point) to the top of a crest

wavelength = the distance from the start of one crest to the start of the next

frequency = the amount of waves which pass through a fixed point every second

Calculating the speed of waves (how much information or energy the wave can carry)

wave speed= frequency x wavelength

(m/s)             (Hz)               (m)

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Properties: Reflection (P1.5.3)

Laws Of Reflection:

• normal is perpendicular to the mirror
• angle of incidence (angle from incident ray to normal)
• angle of reflection (angle from reflection ray to normal)

angle of incidence = angle of reflection

real image = image formed by light rays meeting

virtual image = image formed where light rays seem to come from

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Properties: Refraction (P1.5.4)

refraction = changes speed as it crosses the boudary between two substances                             ( between mediums)

= causing it to change direction

= all types of waves can refract

DOES NOT occur if waves cross the boudary 90° (normal)

air to glass = angle of refraction is less than the angle of incidence

glass to air = angle of refraction is more than the angle of incidence

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Properties: Diffraction (P1.5.5)

diffraction = the spreading out of waves when they pass through a gap or around a

obstacle.

• SMALLER gap means MORE diffraction
• BIGGER gap means LESS diffraction
• when the gap is similar to the wavelength, diffraction is at its biggest!

Signal:

People who live in hilly areas will often get poor reception, because if the radio and microwaves do not diffract enough over the hilly, they will not reach the houses.

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Sound (P1.5.6)

sound waves = longitudinal waves

= can not travel through a vacuum

• something vibrates, causing layers of nearby air to vibrate
• making layers of air further away vibrate
• the object continually pushes and pulls creating compressions and rarefractions
• the waves reach your ears causing ear drums to vibrate
• allowing you to hear sound

echo = reflection of sound

(has to have bare smooth walls --> fabric = absorbs and uneven = sound scattered)

humans can hear sound at a frequency of 20Hz - 20,000Hz

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Musical Sound (P1.5.7)

high amplitude = louder note

high frequency = higher pitched note

resonates = vibrations inside the instrument build up creating a louder sound

when you play an instrument the instrument (and the air inside) vibrates and creates sound

musical notes = rythmic, waves change smoothly, wave patterns repeat

sound = vary in frequency, no pattern

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Key Words (P1.5)

• energy
• transverse
• longitudinal
• transfer
• amplitude
• frequency
• speed
• wavelength
• crest
• trough
• vibrations
• refraction
• refraction
• difraction
• angle of incidence
• angle of reflection
• medium
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