Monday 10/13

Warm UpCopy the transverse wave below and label the parts (1-4)

Agenda1. Warm Up2. Waves – Part II Notes3. Twig – Reflection and

Refraction, Prism

1. Wavelength 2. Amplitude3. Crest 4. TroughWave type: Light

Waves – Part II

Wave Interactions:- Reflection- Refraction- Diffraction- Interference- Standing Waves

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Reflection

Reflection • When a wave hits a surface

that it cannot pass through and bounces off surface

Ex. Ball that bounces off floor in gymSound wave bouncing off canyon wall

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Law of Reflection

Law of Reflection• Law of Reflection states that

the angle of reflection equals the angle of incidence

- All waves obey this law (sound and light)

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Refraction

Refraction • The bending of waves due to a

change in speed between mediums

• When a wave moves from one medium to another medium at an angle, it changes speed as it enters the second medium, which causes it to bend

• Note - all waves change speed when entering new medium – however not all waves will not bend

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Diffraction

Diffraction• The bending of waves around

the edge of a barrier

- When a wave passes a barrier or moves through a hole in a barrier, it will spread out

Ex. When a light enters a prism it will bend light into separate wavelengths

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Interference

InterferenceWhen two or more waves meet, they effect each other which is known as an interference

Two types of interference:- Constructive- Destructive

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Constructive Interference

Constructive Interference

When two waves combine to make a wave with a larger amplitude

Think – construct – “build larger”

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Destructive Interference

Destructive Interference

When two waves combine to make a wave with a smaller amplitude

Think – destructive – “to flatten”

Sound Waves

Remember, sound is a longitudinal wave

It needs to move through a medium (ex. door, wall, water, air)

SONAR – use to locate objects underwater

Speed of Sound

The speed of sound at room temperature (20 c)is 342 m/s

However, it depends on the:ElasticityDensity Temperature Of the material

Elasticity, Density and Temperature

Elasticity – the ability of a solid to return to its original shape after being deformed

Sound moves best in solids that are elastic compared to liquids or gas

Density and Temperature

Density – the amount of matter in a given space

Sound moves slower in denser materials

Pb, Ag > Fe, Steel More Dense > Less Dense

Temperature

Temperature – the measurement of the average kinetic energy of a substance

Higher air temperatures allow sound to move through air faster

Air Temperature C Speed (m/s)

-20 318

-10 324

0 330

10 336

20 342

30 346

Properties of Sound

Pitch – how high or low the sound appears to a person

High pitch – high frequency

Low pitch – low frequency

Doppler Effect

When a moving source appears to have a higher frequency and wavelength when near observer, but a longer wavelength and lower frequency when it moves away

Ex. Ambulance sirens

Doppler Effect