2. Grade 8 Vocabulary List 1
1. wave
2. mechanical
3. electromagnetic
4. amplitude
5. wavelength
6. frequency
7. reflection
8. refraction
9. diffraction
10. pitch
11. resonance
12. overtone
13. eardrum
14. radiant
15. spectrum
16. infrared
17. radiation
18. gamma ray
19. medium
20. lens
21. retina
22. inquiry
** Need to write for each word:
1. Definition
2. Your own sentence
3. _____________________________________________
(Summary for Section 1 of Chapter 16)
(Main Idea)
Waves are a kind of _____________________________ and possess certain properties. There are also
different kinds.
(Supporting Idea 1)
Waves are ____________________ that have rhythm. They carry ____________ but
________________________.
(Details)
Waves can occur in water from running boats. Also, the sound made from a streak of lighting is a wave.
It is important to emphasize that waves cause energy to move –but- no matter moves.
(Supporting Idea 2)
Scientists believe many waves (but not all) work by molecules ____________________. This is a model
only.
(Details)
One molecule has energy. It then passes some energy to the next molecule. That molecule passes it to
another molecule and so on. It is similar to passing a ball.
(Supporting Idea 3)
Mechanical waves always transfer energy through molecules. So they need some
____________________ that has molecules in it to work.
(Details)
For example, water waves work through water molecules. Sound waves travel through almost any solid,
liquid or gas such as air.
(More Details)
One kind of mechanical wave is a ____________________. Here, energy is passed by molecules
moving ________________________ or at right angles to the direction the wave travels. There are
peaks and valleys called crests and troughs. See figure 3 on page 464. The peaks are called crests
and the valleys are called troughs.
(More Details)
Another kind of mechanical wave is a _______________________. Here, molecules move forward and
backward along the direction the wave moves in. See figure 4 on page 464. The molecules move a
little but they always return to the original positions. Only energy travels somewhere. A coiled spring is a
good example.
(Supporting Idea 4)
_______________________ are a common example of compressional waves. They are produced by
something that is vibrating.
(Details)
When some object vibrates, it may first move up. As a result, molecules are pushed closer together.
This is called a compression. Then the object moves down. As a result, the molecules have more room
and spread out and away. This is called a rarefaction. This action is repeated again and again as the
object continues to vibrate going up and down. The series of compressions and rarefactions forms the
sound wave. See figure 5.
4. (Supporting Idea 5)
Electromagnetic Waves _________________________ so they can travel in space.
(Details)
Examples include radio waves, visible light waves and ultraviolet rays. The _______________ also
produces many kinds of electromagnetic waves.
5. SUMMARY – Organizer Handout
(for Chapter 16, Section 2, pg. 467)
Reading Notes
Step 1: Read one time. * Take notes too if you want!
Step 2:
Write the Main Idea (1-2 sentences) –_________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
Step 3: Write the supporting ideas. Write in the small boxes first!
Step 4: Write the supporting details. Write in the bigger boxes later!
Supporting Idea 1 (1-2 sentences)
Supporting Details 1 (1+ sentences)
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
Supporting Idea 2 (1-2 sentences)
Supporting Details 2 (1+ sentences)
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
8. 1 Missing Handout after Computer Crash-
- Summary note on Wave Behavior (Chapter 16, Section 3, page 472)
* see me for these if you need them until I fix this problem. Sorry!
9. What are Electromagnetic Waves?
An electromagnetic wave is a special kind of
wave that is produced by charged particles
in motion. It does not require a medium to
travel in.
How does an Electromagnetic Wave
Work?
An electromagnetic wave carries radiant
energy. Almost anywhere in the universe,
there exists various charged particles such
as electrons or protons. (even in space!)
Charged particles are special because they
are surrounded by electric fields. An
electric field is some kind of force field.
electric field
Ex. a proton
10. As well for certain reasons, a charged
particle may start moving. When a charged
particle starts moving, a second kind of force
field is formed: a magnetic field. (just like
with a magnet)
magnetic field
Ex. an electron
Finally, when a charged particle is moving
up and down, its electric field and its
magnetic field move farther and farther away
in many directions. They also move with a
wave like motion. Eventually, the electric
field may strike another charged particle and
cause it to move. Then, this particle
produces both an electric field and a
magnetic field. In the process, the wave
continues through the movement of its two
force fields. As more and more charge
particles are hit, their vibration extends the
wave and energy thus moves.
(see figure 5 on pg. 523)
11. SUMMARY – Organizer Handout
(for Chapter 18, Section 2, pg. 525)
Reading Notes
Step 1: Read one time. * Take notes too if you want!
Step 2:
Write the Main Idea (1-2 sentences) –_________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
Step 3: Write the supporting ideas. Write in the small boxes first!
Step 4: Write the supporting details. Write in the bigger boxes later!
Supporting Idea 1 (1-2 sentences)
Supporting Details 1 (1+ sentences)
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
Supporting Idea 2 (1-2 sentences)
Supporting Details 2 (1+ sentences)
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
14. (knowledge) The Electromagnetic Spectrum
(for Chapter 18, Section 2, pg. 525)
There is a huge range of electromagnetic waves in any given space. These waves differ according to
their frequencies and wavelengths. Moreover, how short their frequencies and how long their
wavelengths are gives rise to a different type of electromagnetic wave with its own distinct
characteristics.
How Different Types of Electromagnetic Waves are Produced-
Something (ex. an antenna from a radio or tv tower, a star in space, lightning in the sky) cause some
charged particles to move. The energy given to these particles causes them to vibrate at different
speeds. The different speeds of the particle vibration in create electromagnetic waves of different
wavelengths and frequencies that have specific characteristics and uses.
(see Figure 7 on pg. 525 of your textbook for summary diagram)
Types of Electromagnetic Waves-
1. Radio Waves– these are electromagnetic waves having very low frequencies and therefore
very long wavelengths. Their wavelengths are longer that 0.3 m. These waves are used to
transmit both radio signals (that give rise to sound through radio speakers) and tv signals (that
give rise to pictures on tv screens). By changing the wavelength very slightly, you can transmit
radio or tv signals at different frequencies of channels as has been done for radio and tv stations.
2. Microwaves- these electromagnetic waves are shorter than radio waves but still pretty long. Their
wavelengths are between 0.3 m and 0.001 m. These waves are used by cell phones to transmit
sound and even video. Microwave ovens also use them to make food molecules vibrate faster which
warms the food in turn. Radars also work on microwaves. Some device produces them where they
are reflected off of nearby objects and bounce back. The device then measures things like the time
for reflection to determine how close the object and also its location. Bats and dolphins do the same
thing
3. Infrared Waves- these electromagnetic waves have wavelengths between 0.001 and 0.000 007 m.
Because the charged particles for these waves are moving much faster, heat is generated by these
waves. Every object emits infrared waves because all atoms and molecules are in constant
movement which causes their associated charged protons to move too and create waves. Special
instruments called infrared detectors can distinguish objects based on differences in the infrared
waves they produce from other things in their surroundings. Some night visions gadgets work in this
way and certain animals such as pit vipers can detect infrared waves to hunt prey at night.
4. Visible Light- when charged particles are stimulated to generate waves of a higher frequency by a
fast enough vibrating object, not only is more heat produced but light is produce as well. Visible light
has a wavelength between 0.000 007 and 0.000 004 m. By slight changes in a wavelength within this
range, different shades of colour are produced.
5. Ultraviolet Radiation- here waves are produced between 0.000 004 and 0.000 000 000 1 m.
Because the waves are produced by faster vibrating objects, they carry more energy. Consequently,
these waves can damage certain molecules including many molecules that make up living cells.
15. Moreover, too much ultraviolet radiation can kill healthy cells. Sun burn results in this way. Sun
glasses protect you from ultraviolet radiation by reflecting the waves away from your eyes.
One of the best protectors from UV radiation is the earth’s ozone layer. It keeps out most of the UV
radiation from the sun. However, it is being damaged by certain chemicals created by air pollution.
However, a little ultraviolet radiation is actually good for you because it stimulates the production of
vitamin D by your body. Also, UV radiation is important for disinfecting things such as lab equipment.
Sterilizers use UV rays.
6. X rays and Gamma Rays – these electromagnetic waves have extremely tiny wavelengths. As a
result, they carry a lot more energy and can damage many things that they hit. For instance, they can
go right through skin and muscle. Lead can be used a shield for X rays. Gamma rays are produced
from nuclear fusion and fission and cause the greatest damage.
X rays are useful in creating images of the body for doctors because when they pass through the body,
they are absorbed at different degrees due to varying densities of the body. An special image can be
obtained to reflect what a part or region inside the body looks like.Gamma rays can be used to treat
cancer by having them targeted on cancerous tumors. Harmful bacteria can be treated in a similar
fashion.
