Sound and Light

1

The Nature of Light

Waves & Sound

A. Waves

1. The nature of waves

a. A wave is a rhythmic disturbance that transfers energy.

b. All waves are made by something that vibrates.

B. Sound

1. Energy is transferred from particle to particle through matter.

2. How we hear

a. Outer ear collects sound.

b. Middle ear amplifies sound.

c. Inner ear converts sound.

The ear is a very sensitive organ. It senses vibrations

in the air then amplifiesthem and transmits signals to the brain

3. Properties of sound

a. Intensity and loudness

1) Intensity depends on the energy in a sound wave.

2) Loudness is human perception of intensity.

3) Loudness is measured on the decibel scale.

b. Frequency and pitch

1) High frequency means more vibrations hitting the ear.

2) Pitch is how high or how low a sound seems to be.

3) Healthy humans can hear from 20 Hz to 20,000 Hz

4) We are most sensitive from 440 Hz to 7,000 Hz.

This all depends on how the particles can transmit the compressions and rare factions of sound waves

The speed of sound depends

on the medium

The loudness of a sound depends partly on the energy contained in the sound wave .

The intensity of a sound wave describes the rate at which a sound wave transmits energy through a given area of the medium.

The greater the intensity of a sound, the louder the sound will seem

The air column in a clarinet, however vibrates at its fundamental frequency and at certain whole number multiples of that frequency called harmonics.

The sound produced by the guitar will be the loudest when the forced vibrations cause the body of the guitar to vibrate at a natural frequency called resonance.

a) Threshold of hearing (0 db)

b) Threshold of pain (120 db)

5) Ultrasonic sound has a frequency greater than 20,000 Hz.

a) Dogs (up to 35,000 Hz)

b) Bats (over 100,000 Hz)

c) Medical diagnosis 6) Infrasonic sound has a frequency below 20 Hz; they are felt rather than heard

(earthquakes, heavy machinery).

c. Speed of sound

1) 332 m/s in air at 0 C.

2) Changes by 0.6 m/s for every Celsius degree from 0 C.

3) Subsonic – slower

4) Supersonic – faster than sound (Mach 1 = speed of sound)

5) Sonic Boom (skip to1:35)pressure cone)

d. The Doppler effect – the change in pitch due to a moving wave source.

1) Objects moving toward you cause a higher pitched sound.

2) Objects moving away cause sound of lower pitch.

3) Used in radar by police and meteorologists and in astronomy.

4. Musical sound

a. Noise has no pattern.

b. Music has a pattern and deliberate pitches.

c. Sound quality describes differences of sounds that have the same pitch and loudness.

d. Every instrument has its own set of overtones.

e. Beats are pulsing variations of loudness caused by interference of sounds of slightly different frequencies.

5. Uses of sound

a. Acoustics – the study of sound.

Soft materials dampen sound; hard materials reflect it (echoes and

reverberations).

b. SONAR – Sound Navigation and Ranging (echolocation).

c. Ultrasound imaging

d. Kidney stones & gallstones.

A sonar works by measuring the time it takes for sound waves to be reflected back from a surface.

Ultra sound imaging is used in medicine. Using sonograms, doctors can safely view

organs inside the body without having to perform surgery.

Sonograms can be used to diagnose problems, to guide surgical procedures, or even to view unborn fetusus.

Sound and Light

17

Light Diffracts like a wave Light also reflects and refracts

Sound and Light

18

Nobel prize winners in physics Discovered that light, which

usually travels in waves, sometimes behaves as if it were made up of a stream of small quantities, or quanta, of energy

Sound and Light

19

Small unit of light energy or electromagnetic radiation. “Packets”

No mass, bundle of energy. The energy, E, of a photon is

calculated using the equation E = h, Where h is Planck's constant and

is the frequency of the light.

Sound and Light

20

Sound and Light

21

Absorbs Energy

Explains why light can travel through the vacuum of space

Light can knock electrons off a metal plate

Duality Different characteristics depending on the

situation Scientists use different models depending on what

they are studying

Sound and Light

22

Sound and Light

23

In a vacuum it is called ‘c’

Depends on the medium

Sound and Light

24

Sound and Light

25

Where you are:

Source of light:Time to get there:

Home Plate

Outfield fence 125m (410ft)

½ of a millionth of a second

Soccer goal

Other goal 100m (328ft)

1/3 of a millionth of a second

Earth Moon 376,280km 233,810 miles

1 ¼ seconds

Sound and Light

26

Earth

Sun 150,000,000 km (93,000,000 miles)

8 1/3 minutes

Earth

Proxima Centauri, the nearest star 41,000,000,000,000 km

4 1/3 years

Where you are:

Source of light:

Time to get there:

The rate at which light energy flows through a given area of space is referred to as its intensity.

Light waves spread out spherically from the source

Therefore intensity will drop as distance increases

Sound and Light

27

Sound and Light

28

System that uses reflected radio waves

Determine distance, location, shape and speed

Sound and Light

29

Reflection and Color

Sound and Light

31

Sound and Light

32

Sound and Light

33Diffuse reflection

States that when light rays reflect off a surface the angle of incidence equals the angle of reflection.

Sound and Light

34

' Ө = Angle of

incidence

Ө’ = Angle of

reflection

The theoretical line perpendicular to the surface where light hits a mirror.

Sound and Light

35

An image that results from an apparent path of light rays

Appears behind a mirror Or in front of a lens

REAL IMAGE: Light rays really exist at

the point where the image appears. Appears in front of a mirror. Or through a lens.

Sound and Light

36

Sound and Light

37

Can create real images

Sound and Light

38

Sound and Light

39

Objects have color because they reflect certain wavelengths of light

The object absorbs all the other colors

Your brain interprets each wavelength as color

Sound and Light

40Reflection of Green Light by Leaves

Sound and Light

41

A black flower with green leaves

Sound and Light

42

Sound and Light

43

Light PigmentAdditive Subtractive

Sound and Light

44

Sound and Light

45

Sound and Light

46

Refraction, Lenses and Prisms

Sound and Light

47

Bending of light rays From one medium to

another Due to changing

speeds

Sound and Light

48

When light moves from a material in which its speed is higher to a material in which its speed is lower, it is…

Bent toward the normal.

_________________________________ If a light moves from a material in which

its speed is lower to one in which its speed is higher,

The ray is bent away from the normal

Sound and Light

49

Creates mirages (Aurora Borealis) Are a virtual image Heat leads to diffraction that bends the

light toward the sky

Sound and Light

50

Light enters one end of a fiber optic cable and exits the other end

Complete reflection Between two mediums Angle of incidence exceeds the

critical angle

Sound and Light

51

Sound and Light

52

Sound and Light

53

Sound and Light

54

Sound and Light

55

Concave Lens It bends light outward and can only create a

virtual image.

Sound and Light

56

Sound and Light

57

the cornea is responsible for the largest percentage of light refraction

Sound and Light

58

Sound and Light

59

The effect in which white light separates into different colors

Due to changes in wave speed of the different colors

Rainbows are Caused by dispersion & internal reflection

Sound and Light

60

Sound and Light

61

Sound and Light

62

Pg. 480-482 1-24, 30, 38Pg. 483 1-9

Pg. 520-522 1-23, 25, 37Pg. 523 1-7

Copy the question and Complete answers