Page 115
S8P4.
Waves
What is a wave and how does light and sound transfer energy from one
place to another?
A wave is a rhythmic disturbance that transfers energy
through matter or space WITHOUT transferring matter.
Waves can be categorized by whether or not they
require a medium. A medium is matter that waves
sometimes travel through. A medium can be a solid,
liquid or gas. Water is the medium for ocean waves
and air is the medium for sound waves.
A mechanical wave is a wave that requires matter.
Examples – ocean waves, sound waves, and seismic
waves
An electromagnetic wave is a wave that does not
require a medium even though it can have one.
Examples- radio waves, microwaves, and visible light.
On page 114 – Classify each of the following examples of waves as either
mechanical waves or electromagnetic waves in a 2-column table.
Ocean, light, radio, television, seismic, sound, microwaves, gamma
radiation, ultraviolet, tidal waves
Mechanical
Electromagnetic
Page 11
Waves can also be categorized by how they move.
A wave that transfers energy in a direction
perpendicular (at a right angle) to its medium
is called a transverse wave.
A transverse wave is made of high points called
crests and low points called troughs. Ex. –
ocean waves
A wave in which the particles vibrate back and
forth (parallel) along the path that the wave
moves is known as a compressional wave or
longitudinal wave.
Compressional waves are made up of areas where
the particles are crowded together called
compressions and areas where the particles
are spread out called rarefactions.
Top half of page 116 – Transverse wave illustration with properties
Bottom half of page 116 – Compressional (longitudinal) wave illustration
with properties
Page 11
A wave in which the particles vibrate back
and forth along the path that the wave
moves is known as a compressional wave
or longitudinal wave.
Compressional waves are made up of areas
where the particles are crowded together
called compressions and areas where the
particles are spread out called rarefactions.
Compressional waves move parallel to the
direction the particles are moving.
Top half of page 120 –
Bottom half of page 120 –
Wavelength – the distance between two adjacent crests or two adjacent
troughs of a transverse wave.
Frequency – the number of wavelengths that pass a given point in one
second; it is measured in a unit called Hertz.
Wavelength and frequency are directly related. The longer the
wavelength, the lower the frequency. The shorter the wavelength, the
higher the frequency.
A high frequency wave has high energy. A low frequency wave has low
energy.
On page 122 – copy Figure 6 and the caption located on page 494 of the
textbook.
Pages 122 - 123
The electromagnetic spectrum is the range of all possible electromagnetic waves
(radiation) with different frequencies and wavelengths. Electromagnetic waves
can travel through matter or space.
Pages 122 - 123
Ex. radio,
television, cell
phones
Ex. microwaves,
radar
Ex. remote
controls,
some snakes
ROYGBIV
The electromagnetic spectrum is the range of all possible electromagnetic waves
(radiation) with different frequencies and wavelengths. Electromagnetic waves
can travel through matter or space.
Ex.
Ex. bone Ex.
sunlight images nuclear
reactions
Page 125
S8P4b. & S8P4d.
Wave Behavior
Why is it difficult to grab items from the bottom of a swimming pool? Why
do straws in glasses appear broken?
Waves can change direction when they encounter
matter. They can reflect, refract and/or diffract. Waves
can also interfere with one another.
Reflection - A wave is reflected when it strikes (hits)
matter and bounces off of the matter. The smoother
the surface that it hits, the clearer the reflected wave.
The rougher the surface, the more distorted the image.
An image in a mirror is a reflected light wave. An echo
is a reflected sound wave.
According to the law of reflection for a smooth surface,
the angle of incidence is equal to the angle of
reflection.
On page 124 - Reflection
Using the image, what do you think these terms mean?
- Incident ray - Reflected ray - Angle of incidence - Angle of reflection -
On page 124 - Reflection
Using the image, what do you think these terms mean?
- Incident ray – the wave source (the beam of light from the flashlight)
- Reflected ray – the reflected wave (the light that bounces off the surface)
- Angle of incidence - the angle the incident wave strikes the surface
- Angle of reflection - the angle the reflected wave bounces off the surface
Page 12
Refraction – A wave is refracted when it bends as
it passes from one medium to another (one
type of matter to another). When a wave goes
from one medium to another, it either speeds
up or slows down depending on the material.
An example of refraction is when a straw
appears broken when in a glass of water.
Another example is when it is difficult to pick
up items from the bottom of a pool.
When white light is refracted it can be separated
into its component colors (ROYGBIV).
Diffraction – A wave is diffracted when it bends
and/or spreads as it passes through an opening
or around an object.
On top of page 126 – Refraction
On bottom of page 126 –Diffraction
Page 12
Interference – is the combination of two or more
waves that results in a single wave. When
waves combine by interference, the amplitude
of the resulting wave is different from the
amplitude of the original waves.
When the crests of two waves overlap with each
other, the resulting wave has a greater
amplitude than the amplitude of the original
waves. This is called constructive interference.
When the crest of one wave overlaps with the
trough of another wave, the resulting wave has
a smaller amplitude than the original waves.
This is called destructive interference.
page 128
Label A and B as either constructive interference or destructive interference.
original waves
resulting wave
original waves
resulting wave
A
B
Page 131
S8P4.
Wave Behavior
What happens when a substance absorbs light?
Light waves interact with matter by transmission and
absorption. All objects reflect and absorb some light
waves. When light waves strike an object, some of the
waves are absorbed by the object, some are reflected
by it, and some might pass through it.
Materials that let no light pass through are opaque.
You cannot see other objects through opaque objects.
Materials that allow nearly all the light that strikes
them to pass through are called transparent.
Materials that allow only some light to pass through
are translucent. Objects behind translucent materials
are only barely visible.
page 130
Categorize each of the following materials as either transparent, translucent
or opaque in a 3-column table.
Transparent
Translucent
Opaque
Book
Clear window
Scissors
Waxed paper
Whiteboard
Stained glass window
Camera
Camera lens
Pencil
Saran Wrap
Aluminum Foil Frosted glass
magnifying glass lens
glasses lenses bricks
clear light bulb
Speaker
eraser
sweet tea
drinking water
Page 133
The color of an object depends on the light waves
it reflects. An apple appears red because only
red light is reflected back to your eye and the
other colors are absorbed by the object.
The primary colors of light are red, green and
blue. When these colors of light (all colors of
the spectrum) are combined, white light is
produced.
The primary colors of pigment are yellow, cyan
and magenta. When these colors of pigment
(all colors) are mixed together, it forms black.
Summary
Page 135
S8P4.
Sound
What makes a sound wave move faster in hot or humid weather?
A sound wave is a mechanical wave produced by a
vibrating object. Sound waves cannot travel through
empty space or a vacuum. They need matter.
When the object vibrates, it causes the molecules
around it to compress (compression) and expand
(rarefaction) until it reaches your ear.
Sound travels faster through solids than through
liquids and gases. Also, as the temperature increases,
the speed of sound increases and when the air is more
humid, the speed of sound increases.
Summary
Page 137
S8P4.
Sound
What makes a sound softer or louder? What is the difference between a
soprano voice (high) and a bass voice (deep)?
The amplitude is the wave’s intensity (the amount of
energy the wave is carrying). The higher the amplitude,
the more energy being carried and the louder the
sound.
The intensity or volume of a sound is measured in units
called decibels. The higher amplitudes are louder and
have a higher number of decibels. Lower amplitudes
are softer and have a lower number of decibels.
The frequency of a wave affects the pitch. The higher
the frequency, the higher the pitch (Ms. Price’s voice).
The lower the frequency, the lower the pitch (Mr.
Ennis’ voice).
Summary
page 136