Transcript Light and Sound - Bibb County Public School District

Light and Sound
4th Grade Science
EQ: What is light?
It’s a kind of energy called
“electromagnetic (EM) radiation” (but this
kind of radiation is not harmful).
There are other kinds of EM radiation too
(radio waves, microwaves, x-rays, etc.), but
light is the part WE can see, the part that
makes the rainbow.
How does light travel?
• FAST and STRAIGHT
• About 186,000 miles per second , so light
from the sun takes about 8 minutes to go
93 million miles to earth.
• If you could DRIVE to the sun at 60 mph ,
it would take you 177 years to get there!
In one second, light can go around the
earth 7 times!
How are shadows
formed?
• When light strikes an object, some light reflects.
When there is an obstacle in the way of the light,
and it cannot pass, there is no light to reflect, and
thus a shadow is formed.
• A SHADOW IS FORMED WHEN LIGHT SHINES
AT AN OPAQUE OBJECT BLOCKING THE
LIGHT RAY CAUSING A SHADOW BECAUSE
LIGHT ONLY GOES IN A STRAIGHT LINE.
Vocabulary
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Transparent object is one that lets
light pass through. (clear window)
• Translucent objects lets some light go through but not
all (bathroom window)
• opaque: light can not go through it. Impenetrable by light;
neither transparent nor translucent.
Example: opaque object lets no light pass through-( table)
• absorption: refers to the physical process of absorbing
light. The process in which incident radiated energy is
retained without reflection or transmission on passing
through a medium.
For example, light can not go through an object that is
opaque because that object absorbs the light.
Refraction
• http://ilovenewton.com/wpcontent/uploads/2012/05/interferen
ce_refraction_reflection300x225.jpg
Sound energy
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Sound is a type of energy made by vibrations. When any
object vibrates, it causes movement in the air particles.
These particles bump into the particles close to them, which
makes them vibrate too causing them to bump into more air
particles. This movement, called sound waves, keeps going
until they run out of energy. If your ear is within range of
the vibrations, you hear the sound.
• Pitch: the frequency at which an object vibrates to create a
sound.
A tuning fork, for example, that vibrates 440 times a
second will produce a perfect “A” note. It is these
predetermined levels of frequencies that pitch is
categorized into the twelve chromatic musical tones.
vibrate: move back and forth
rapidly.
• Did you hear that sound? It was made by air vibrating. The
same is true for sounds made by musical instruments. The
difference between NOISE and MUSIC is that musical
sounds are organized into patterns that have pitch and
rhythm. Noise is just random, disorganized sounds. Sounds
are made and travel in the same way whether they are
musical sounds or noise.
• A musical sound is called a tone, and is produced by
air vibrating a certain number of times per second. These
vibrations are called waves.
EQ: What is sound?
• Sound is a form of energy, just like electricity
and light. Sound is made when air molecules
vibrate and move in a pattern called waves, or
sound waves.
• Think of when you clap your hands, or when you
slam the car door shut. That action produces
soundwaves, which travel to your ears and then to
your brain, which says, “I recognize that sound.”
• This is from Science Kids at Home.
SOUND
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Sound is a type of energy made by vibrations. When any object
vibrates, it causes movement in the air particles. These particles
bump into the particles close to them, which makes them vibrate
too causing them to bump into more air particles. This movement,
called sound waves, keeps going until they run out of energy. If
your ear is within range of the vibrations, you hear the sound.
Picture a stone thrown into a still body of water. The rings of
waves expand indefinitely. The same is true with sound. Irregular
repeating sound waves create noise, while regular repeating waves
produce musical notes.
When the vibrations are fast, you hear a high note. When the
vibrations are slow, it creates a low note. The sound waves in the
diagram show the different frequencies for high and low notes.
Low frequency notes High frequency notes
Low Frequency Notes
High Frequency Notes
Quiz
1.
The bending of a wave caused by the
change of speed that occurs when the
wave passes from one medium into
another is __________.
2. The bouncing back of a wave off an
object or surface is ______________.
3. Describes materials that let nearly
all the light rays that hit them pass
through _______________.
4. Describes materials that let some
light rays pass through but scatter
some of the other rays is ________.
5. Describes materials that do not let
any light pass through them ______
Directions: Put a T for
true and an F for false
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___ Light is electromagnetic radiation.
___ Opaque objects can either absorb or reflect light.
___ Transparent substances reflect light.
___ A convex lens is curved outwards.
___ A prism is a type of lens
___ You can see your reflection on an opaque object
___ The visible spectrum is light you can see.
___ All light passes through translucent objects.
___ A concave lens is like the inside of a sphere.
___ Refraction means the light stops.
answers:
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F