Unit 6 Waves

Unit 6
Waves

Why learn about waves?

Waves are all around us

● The light in this room and the sound you hear
● The ripples in the water
● The electricity flowing through wires

Why learn about waves?

Three of your 5 senses respond to waves

●

Hearing

●

Sight

●

Touch

Where can you find waves?

●

Whenever information, energy or motion is transmitted over a
distance without any obvious moving.
○ Remote controls/video game controller
○ Cell Phones
○ TV, Radio, Internet
○ Light (visible), infrared, ultraviolet, etc.

What is a Wave?

Wave- traveling oscillation that has frequency,
wavelength and amplitude

Waves carry oscillations from one point to another

Waves transfer energy, but the material remains undisturbed

There Are Different Types Of Waves

Types of Waves

●

Mechanical waves travel through a medium and require a
connection.

• Example - A wave will pass along a string because it is
  continuous, however if the string was broken then the wave
  would NOT pass through the break

●

Electromagnetic (radiant) waves do NOT require a medium

• Example – light from the sun travels through space to earth.

Multiple Choice

Waves in water is an example of a ...

• Mechanical Wave

• EM Wave

Types of Waves

● Transverse cause a wave to travel perpendicular

to the direction of the wave.

● Longitudinal cause a wave to travel parallel to

the direction of the wave.

The Motion of Waves: Linear vs. Harmonic

Linear- motion from one place to another with no
repeating

Harmonic Motion- motion that repeats in cycles

Multiple Choice

An oscillating fan is an example of ...

• Linear motion

• Harmonic motion

Wave Shapes Vocabulary

● Crest- high point of wave/ also called wave

fronts

● Trough-low point of wave

Wave Shape Vocabulary

● Cycle- one unit of harmonic motion
● Oscillator- physical system that has

repeating cycles

● Period- time it takes to complete one

cycle (T) unit: seconds

● Frequency – number of complete

cycles per second (f) unit: 1/seconds
(Hz)

Wave Properties

● Frequency- how often a wave pulse passes by a

certain point
○ Measured by looking at one point and see how often it

oscillates in a unit a time

○ The wave carries the same frequency to every point it

reaches

○ Measured in Hertz (Hz)

Frequency

Wave Properties

● Period (T) and Frequency (f) are related

T=1/f

● Damping- gradual loss of amplitude due to

friction

Wave Properties

● Amplitude- largest amount that goes above or

below average- “size of wave”
○ Example: The amplitude of a water wave is the

maximum height the wave rises above the
level surface.

○ Formula: Amp= ½(high value-low value)

Wave Properties

● Wavelength- symbol λ (unit is meters)

○ is the distance from any point on a wave to the

same point on the next cycle of the wave.

○ The distance between one crest and the next crest is

a wavelength.

Wave Properties

● Speed (v)- how fast a wave can transmit an

oscillation from one place to another
○ Calculated as v= fλ
○ Unit is m/s

Wave Behavior: Interference

Occurs when 2 or more waves come together in the same medium
● Constructive interference- when wave pulses come

together and combine to make one large force

● Destructive interference- when wave pulses come together

and make a smaller amplitude

After interfering, they continue on their paths as if nothing happened

Wave Shapes

● Plane wave- has a wave front

that is a straight line and is
perpendicular to the direction of
the wave movement.

● Circle waves- radiate outward

from the center.

Waves and Light

Electromagnetic Spectrum

Application of wave properties
● How radiant energy is classified
● The bands of the spectrum are arranged by frequency and wavelength

• Higher frequency, shorter wavelength

• Radiant energy in a vacuum travels the same speed

● The only portion of the spectrum that humans can see is

the visible light spectrum

Dropdown

The higher the frequency the ​

Select answer

the wavelength

The higher the frequency, the ​

Select answer

the energy

What do you need to know about the EM spectrum?

● The higher the frequency, the shorter

the wavelength (inverse)

● The higher the frequency, the higher

the energy (direct)

What do you need to know about the EM spectrum?

● Gamma rays have the highest frequency,

radio waves the lowest frequency.

● In the visible light region, red has the lowest

energy, violet the highest energy

● All regions of the spectrum travel the same

speed (3 x 108 m/s)

EM Spectrum Calculations

○ v= fλ

v=speed (m/s)

f=frequency (Hz)

λ=wavelength (m)

EM Spectrum Calculations

○ v= fλ

v=speed of light (3x108 m/s)

f=frequency (Hz)

λ=wavelength (m)

Example: Calculate the frequency of a wave that has
a wavelength of 0.10 m.

Multiple Choice

Calculate the frequency of a wave that has
a wavelength of 0.10 m.

• 3 x 10⁹ Hz

• 3 x 10⁸ Hz

• 3 x 10⁷ Hz

• Cannot be solved

EM Spectrum Calculations

○

v= fλ

Example: Calculate the frequency of a radio wave that measures
200 meters.

Example: Calculate the wavelength of a microwave that has a
frequency of 2 x 1010 Hz.

Compare the radio and microwave. Which has more energy?
Which has a larger frequency? Which has a larger wavelength?

Optics

Reflection

● Reflection- wave bounces off and goes in new direction- wavelength and frequency unchanged

- Example: Mirrors and echoes

Refraction

● The wave can pass straight into and through
the obstacle, changing
speed and bending
through the new medium

• Ex: lenses

Diffraction

● wave bends around or through the obstacle or through openings

Example: https://www.youtube.com/watch?v=2TMR-EyF_ds&ab_channel=pmalcolmturner

Classify the following examples based on wave behavior.
(NEW SLIDE)

1.

A fish appearing further away than what it is.

2.

Hearing the radio play through the door to another room.

3.

Seeing the moon due to the sun’s light bouncing off of the
surface.

4.

Shining a flashlight at the mirror and seeing the light on
another object.

5.

A prism separates white light into the rainbow of colors.

Absorption

● Can occur with wave interactions with

materials and boundaries

● The new material may absorb some energy of

the wave by transforming it to another form of
energy (Usually thermal energy)

● Absorption of Light Video https://www.youtube.com/watch?v=VwNKPgo3oxA&ab_channel=EdmundScientific

Radiant Energy

● Does not need a medium for travel
● Travels in all directions
● Organized by wavelength and frequency into the electromagnetic spectrum

Radiant Energy Encounters Materials

● It exhibits the same wave behaviors like

reflection, refraction, diffraction, interference
depending on the type of material

● Materials are then classified by how light interacts

with it

Classification of Materials-Transparent

Transparent- light is allowed to pass
through with minimal reflection or absorption

•Results in a clear image

Classification of Materials-Translucent

Translucent- some light is allowed to pass through

•Light changes directions many times as it passes through
and is scattered
•Results in a fuzzy or unclear image

Classification of Materials-Opaque

Opaque- little if any radiant energy is allowed in
the material it is either absorbed or reflected

•Results in no image

Reflection off of a surface

● Rough surfaces- reflection in all directions

resulting in a diffuse reflection

● Smooth shiny surfaces- reflections result in

clear images

Sound Waves

Sound

● Mechanical wave (LONGITUDINAL)
● Does need a medium for travel
● Goes through all of the same

behaviors

● Speed of sound is slower than light

○ 343 m/s vs. 3x108 m/s

Doppler Effect

● Similar to frame of reference- waves are perceived

differently depending on your location to the source

● The source of the waves produces the waves at the same

frequency, but is perceived differently by observers
○

Those further away from the source perceive a lower frequency

○

Those closer perceive a higher frequency

● Can occur with any type of wave source

Doppler Effect Examples

● Red shift/ blue shift of radiation emitted by

galaxies

● Race cars on a raceway
● Water waves

Breaking the Sound Barrier