Sound

1
Sound Light

• Chapter 15

2
Sound

• Sound waves are caused by vibrations, and carry
  energy through a medium.
• Sound waves are longitudinal waves.
• Speed of sound depends on the medium.

3
Speed of Sound

• Speed of sound at room temperature is about 346
  m/s.
• An increase in temperature increases the speed of
  sound.
• Sound waves travel faster in liquids solids
  than gases.

4
Loudness determined by Intensity

• Intensity of a sound wave describes the rate at
  which a sound wave transmits energy through a
  given area of the medium.
• Loudness depends on the intensity of the sound
  wave.
• The greater the intensity, the louder the sound.

5
Relative Intensity

• The relative intensity of sounds is found by
  comparing the intensity of a sound with the
  intensity of the quietest sound a person can
  hear.
• Relative intensity is measured in units called
  decibels.

6
Pitch

• The pitch of a sound is related to the frequency
  of sound waves.
• High pitch correspond to a high frequency, and
  low pitch corresponds to a low frequency.

7
What type of wave is sound?

1. longitudinal
2. seismic
3. surface
4. transverse

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21 22 23 24 25 26 27 28 29 30
8
Human Hearing

• Infrasound is sound that has a frequency below
  human hearing.
• Ultrasound is sound that has a frequency above
  human hearing.

9
Musical Instruments

• Fundamental frequency is the frequency of a
  standing wave which wavelength is twice the
  length of a string on an instrument.
• Instruments vibrate at their fundamental
  frequency and whole-number multiples of that
  frequency called harmonics.

10
Instruments Amplify Sound

• Vibrations from plucking strings of an instrument
  are called forced vibrations.
• The body of a guitar vibrate at certain specific
  frequencies called natural frequencies.

11
Resonance

• Resonance is when an instrument vibrates at its
  natural frequency.
• The natural frequency of an object depends on
  its
• Shape
• Size
• mass

12
Hearing

• Sound passing through the outer ear to the middle
  ear.
• The middle ear consists of the hammer, anvil
  stirrup.
• The middle ear vibrates the fluids in the
  cochlea.
• The cochlea has tiny hairs that are stimulated
  and transmit the impulses to the brain.

13
Application of Sound

• Sonar is a system that determines distance by
  measuring the time it takes for sound waves to be
  reflected back from a surface.
• Ultrasound is a device that uses the echoes of
  high frequency ultrasound to produce images of
  internal organs.

14
Assignment

• Design an musical instrument from materials you
  have at home.
• Classify it as a woodwind, brass, percussion or
  string instrument.
• Be able to explain the theory behind the
  instrument playing different tones.
• Be able to present music and play it on the
  instrument in a recognizable way.
• Due Monday.

15
Light as a Wave

• Light travels as transverse waves.
• Light does not require a medium.
• Light waves are called electromagnetic waves.
• The wave model is supported because light can
  reflect, refract and diffract.

16
Light as a Particle

• In the particle model, light travel in photons.
• Photons are considered particles.
• Photons dont have mass, they are bundles of
  energy.

17
Frequency of Light

• The amount of energy is proportional to the
  frequency of the corresponding electromagnetic
  wave.
• A photon with twice as much energy corresponds to
  a wave with twice the frequency is in the
  ultraviolet range.
• A photon with half as much energy corresponds to
  a wave with half as much frequency is in the
  infrared range.

18
Speed of Light

• Light travels at the speed of 300,000 km/s.
• Light travels fastest in a vacuum and slower in
  any medium.
• Nothing travels faster than light in our
  universe.

19
Intensity of Light

• The brightness of light depends on the intensity
  of the light.
• Intensity depends on the amount of light that
  passes through a certain area of space.
• Light spreads out from the source. The farther
  from the light source, the dimmer the light.

20
Electromagnetic Spectrum

• Electromagnetic spectrum consist of light of all
  possible energies, frequencies and wavelengths.
• Ultraviolet light has higher energy and shorter
  wavelengths than purple light.
• X-rays has higher energy and shorter wavelengths.
• Gamma rays has the highest energy and shortest
  wavelengths.

21
Electromagnetic Spectrum continued

• Infrared waves has wavelengths slightly longer
  than red light.
• Microwaves are used for cooking.
• Radio waves have the longest wavelengths.
• Radar is used to determine location.

22
Reflection and Color

• Reflection occurs as light hits a barrier and
  bounces off of the barrier.
• The incidence ray is the incoming light waves.
• The reflected ray is the light waves that bounce
  off of the barrier.

23
Reflection (continued)

• The angle of incidence is defined by the angle
  between the normal and the incidence ray.
• The angle of reflection is defined by the angle
  between the normal and the reflected ray.
• The law of reflection states that the angle of
  incidence is always equal to the angle of
  reflection.

24
Types of Reflection

• Smooth reflection occurs when the light waves hit
  a smooth surface.
• Diffuse reflection occurs when the light waves
  hit a rough surface and the light waves are
  scattered.

25
Types of Mirrors

• Concave mirrors are mirrors that curve inward.
  These type of mirrors can produce virtual real
  images.
• Convex mirrors are mirrors that bulge outward.
  These type of mirrors can produce virtual images.
• Plane mirrors produce virtual images.

26
Type of Images

• Real images are inverted images formed where rays
  of light meet.
• Virtual images are upright images formed where
  rays of light appear to meet or come from.

27
Colors

• The color we see is the light being reflected
  from the object.
• Additive primary colors are red, green blue.
• Subtractive primary colors are yellow, cyan and
  magenta.

28
Colors and Pigments

• If all colors are reflected, you see white light.
• If all colors are absorbed, you see black.

29
Refraction

• Refraction happens when light waves changes speed
  as it goes through different mediums.
• As light waves change speed the waves bend.

30
Effects of Refraction

• Refraction makes objects appear to be in
  different positions.
• Refractions in the atmosphere creates mirages.

31
Snells Law

• Snell's Law Snell's law (also known as Descartes'
  law or the law of refraction), is a formula used
  to describe the relationship between the angles
  of incidence and refraction, when referring to
  light or other waves, passing through a boundary
  between two different media, such as air and
  glass.

32
Total Internal Reflection

• If the angle at which light rays meet the
  boundary between two mediums becomes small
  enough, the rays will be reflected as if the
  boundary were a mirror.
• This angle is called the critical angle, and this
  type of reflection is called total internal
  reflection.

33
Lenses

• A lens is a curved piece of glass.
• Lenses can magnify images.
• Magnification is any change in the size of an
  image compared with the size of the object.

34
Type of Lenses

• Converging lens bends the light inward that
  produces a virtual or real image. (convex lens)
• Diverging lens bends the light outward and can
  produce only a virtual image. (concave lens)

35
Prisms

• Prism is a triangular shaped piece of glass that
  refracts light.
• Prism disperse light.
• Dispersion is the separation of light into
  separate colors because of the differences in
  wave speed.