1.2 ANALYSING REFLECTION OF WAVES

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Light

Convex water surface

Light is converged (refracted)

Bright

Concave water surface

Light is diverged (refracted)

Dim

Waterfronts

(crest)

Ripple tank

Water

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1.2 ANALYSING REFLECTION OF WAVES

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Reflection of waves• Occurs when a wave strikes an obstacle.

• The phenomenon obeys the Laws of Reflections.

i) the angle of incidence = the angle of reflection

ii) the incidence wave , the reflected wave and the normal lie in the same plane.

• the incidence wave = wave before reflection

1. Reflection (plane wave) by plane reflector

Plane reflect

or

Vibrator

Sponge

Motor

Water

Ripple tank

Compare the wave characteristics before and after reflection

Aspects:

• Wavelength/frequency

• Wavefront shape

• Direction

• The angle

• Velocity

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Comparison Wave Reflection

Aspects Before & after reflection

Wavelength Same

Frequency Same

Speed Same

Direction changed

Wave front shape same

Velocity changed

How to draw the wavefront which reflected by plane reflector

1. Draw the direction of the incident waves

2. Draw the NORMAL line

3. Draw the direction of reflection waves. Make sure the angle i = r

4. Draw the wavefront of reflection waves that perpendicular to it direction

i r i r

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2. Reflection (plane wave) by convex reflector

Convex

reflector

Compare the wave characteristics before and after reflection

Aspects:

• Wavelength/frequency

• Wavefront shape

• Direction

• VelocityNext

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Concave

reflector

How to drawing the wavefront which reflected by concave reflector

?Guide

1. Draw the direction of incident wave

2. Draw the NORMAL

3. Draw the direction of the reflection waves. Make sure the angle i = r

4. Draw the wavefront of reflection waves that perpendicular to it the direction

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ri

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3. Reflection (circle wave) by plane surface

Compare the wave characteristics before and after reflection

Reflect

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Guide

Note

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a

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Questions