Science Notes Unit 2: Waves and Electromagnetic Radiation
Lesson 1 - Wave Properties
Oct 23, 2025
Wave - 1. A disturbance that transfers energy from place to place 2. The movement of energy through body of water
Mechanical Wave - A wave that requires a medium through which to travel
Medium - The material through which a wave travels
Electromagnetic Radiation - The energy transferred through space by electromagnetic waves
Transverse Wave - A wave that moves the medium at right angles to the direction in which the wave travels
Amplitude - 1. The height of a transverse wave for the center to a crest or trough 2. The maximum distance the particles of a medium move away from their rest positions as a longitudinal wave passes through the medium
Longitudinal Wave - A wave the medium in a direction parallel to the direction in which the wave travels
Wavelength - The distance between two corresponding parts of a wave, such as the distance between two crests
Frequency - The number of complete waves that pass a given point in a certain amount of time
The more amount of waves, the faster it is traveling
Vacuum - A space that is completely empty of solids, liquids, gasses, or any other matter.
New ripples are greater in height in original ones
Video:
Wave energy everywhere
Lights: Light waves (electromagnetic spectrum-visible light. Makes it possible to see each other. Does not need a medium
Radio Waves: Also part of the electromagnetic spectrum. Send signal to audio energy to the system (in cell phone) Longest Wave Length and Lowest Frequency
Wave parts -Crest - high point on the wave
Trough - low point on the wave
Amplitude - the distance of the waves from the top or bottom to the center
Microwaves:
Between Ultraviolet and Infrared waves is where we see color
Absorb white light
Reflects the wave length associated with the color
Black absorbs the sun. Doesn’t reflect it
X-rays:
Gamma-rays: Shortest wavelength=Highest Frequency
Electromagnetic waves can travel without a medium
Transfer energy
Oct 24, 2025
A transverse wave travels perpendicular to the direction of the sources motion
Curved shape of the rope shows the main features of a transverse wave
Electromagnetic waves (ex: sunlight) are also transverse waves
Longitude waves travel in the same direction as the vibrations that produced it
Sound is a longitudinal wave
Compressions are the compressed thingies
Rarefactions are the gaps between the compressions.
Energy moves right along the slinky (spring toy)
Surface waves are longitude and transverse waves combined (Ex. ocean waves travels the surface of water)
Oct 28, 2025
Wave speed = Wavelength x Frequency
Waves transmit energy from place to place
Larger amplitude vibrations transmits more energy
Wave’s energy is directly proportional to frequency (Frequency of the wave doubles, the energy doubles.)
Waves energy is measured in joules (J)
Nov 4, 2025
The energy for a wave is proportional to the square of the amplitude
Just like how the parts of a wave are, (crest and trough), in a longitudinal wave, the parts are compression (for the maximum part) and the refraction (for the minimum part)
Lesson 2 - Wave Interactions
Nov 11, 2025
Refraction - When waves bend from one medium to another based on changes due to speed
Reflection - When light, sound or heat waves bounce off a surface and create an image or echo
Diffraction - When waves begin to bend or spread out as they pass through an opening or around an obstacle
Absorption - When waves transfer its energy into another medium or object. It can sometimes convert the energy into thermal energy
Waves travel differently depending on the type
Nov 13, 2025
Constructive Interference - when two waves of similar sizes collide and form a wave greater than both of those waves
Destructive Interference - When two waves make a wave with a smaller amplitude than either of the original waves had
Video Notes- Standing Waves
Standing waves- A wave that remains at a fixed position, created by the interference of two waves of the same type, traveling in opposite directions
Some waves confined to specific region
Playing a harp
Multitude of waves cycles in both directions
Transverse standing waves
Transverse standing waves - can only have particular frequencies
Number of half-wavelengths for any standing waves is quantized
Contains nodes and anit-nodes
Node- points with zero amplitudes (completely stationary)
More nodes means more energy
Anti-nodes- points with maximum amplitude
Two dimensional standing waves- on flat 2 dimensional surface
Nodes are lines and curves (looks like a very oddly cut pizza)
Can be radial and angular nodes
Radial nodes - 2 dimensional (from center to edge)
Angular nodes -
One dimensional waves
Nodes are points (lemon or eye shaped)
Standing waves combine to produce the constant intervals in music
Nov 14, 2025
Resonance is an increase in an amplitude of a vibration which happens when external vibrations match an object’s natural frequency
Motion vibration (shaky shaky)
As the source is moving away, the frequency and amplitude decrease
Resonance Video Notes
Natural frequency- The frequency at which an object oscillates after an initial disturbance
Frequency increases then amplitude increases
Resonance occurs when the driving frequency is equal to the natural frequency
Amplitude increases dramatically
Even if you increase the frequency, the amplitude, spring, wont go beyond its maximum point (NATURAL FREQUENCY)
Reaching maximum amplitude and/or natural frequency is called Resonance
Frequency of driving force matches frequency of natural force?
Swing example: (wtf do we put here?)
Standing waves occur in an object when it vibrates at a natural frequency
Lesson 3 - Sound Waves
Dec 2, 2025
Loudness - the perception of the energy of a sound
Intensity - the amount of energy per second carried through a unit area by wave
Decibel - a unit used to compare the loudness of different sounds
Pitch - a description of how a sound is perceived as high or low
Doppler Effect - the change in frequency of a wave as its source moves in relation to an observer
Differentiate - to identify the difference between
All sound waves begin with a vibration
Sound waves are mechanical waves that need a medium to travel through
The compressions and rarefactions travel through the air
Sound waves travel better through liquids and solids
Ex: when you set a glass down on a table, the sound waves that are generated travel first through the glass and the table and then are released into the air
Sound waves can be longitudinal
They also can be absorbed, reflected, transmitted, and diffracted
Sound waves also pass through a surface called transmitted waves
Sound waves bounce off a surface called reflected waves
Sound waves can also absorb noise
Ex: in some theaters and shows, they use sound panels on the walls to absorb the sound
They do this to improve the listening quality
Sound waves can bend around the edges of an opening
Ex: a doorway
When sound waves travel through air and hit a solid surface, most of the energy is reflected back towards the source
Factors that affect the speed of sound
Stiffness
sound waves travel faster in materials that are harder to compress
This happens because of the movement of one particle will push on another
Sound travels faster in stiffer solids
Density
Refers to how much matter or mass there is in a given amount of space
denser the material, the more mass it has in a given volume (greater in inertia)
Objects with greater inertia accelerate less from an energy disturbance
materials of the same stiffness, sound travels more slowly in the denser material
Temperature
FOR SOLIDS: an increase in temperature reduces the stiffness, so the sound speed decreases
FOR FLUIDS: the increase in temperature reduces the density, so the sound speed generally increases
How loud a sound is depends on the energy and intensity of the sound waves
Ex: If someone knocks lightly on your front door, then you might hear a quiet sound. If they pound on your door, then you hear a much louder sound
This happens because the pounding transfers much more energy through the door than a light knock does
A hard knock on a door produces a much greater amplitude in the sound waves than a softer knock does
The closer the sound wave is to its source, the more energy it has in a given area
When the sound wave moves away from the source, the wave spreads out and the intensity decreases
Every 10-decibel increase represents a tenfold increase in intensity and power
Ex: when loudness increases from 20 to 30 decibels, a sound’s power is multiplied by 10
If loudness increases by 10 again, power increases by another factor of 10
When loudness increases from 20 to 40 decibels, power increases by a factor of 100
frequency of a sound wave depends upon how fast the source of the sound is vibrating
Ex: when people speak or sing, the air from their lungs moves past their vocal cords and makes the cords vibrate
This produces sound waves
Pitch depends on the frequency of sound waves
High frequency, high pitch. Low frequency, low pitch
Change in pitch occurs because the movement of the source of the sound causes a sound wave to either compress or stretch
This leads to the doppler effect
Doppler Effect: the change in the frequency of a sound or light wave when the source of the wave is moving relative to an observer
Lesson 4 - Electromagnetic Waves
Dec 4, 2025
Electromagnetic waves- A wave made up of a combination of a changing electric field and a changing magnetic field.
Electromagnetic spectrum- The complete range of electromagnetic waves placed in order of increasing frequency.
Radio waves- electromagnetic waves with the longest wavelengths and lowest frequencies
Microwaves- electromagnetic waves that have shorter wavelengths and higher frequencies than radio waves
visible light- electromagnetic radiation that can be seen with the unaided eye
Ultraviolet rays- electromagnetic waves with wavelengths shorter than visible light but longer than x-rays
Infrared rays- electromagnetic waves with shorter wavelengths and higher frequencies than microwaves
X-rays- electromagnetic waves with wavelengths shorter than ultraviolet rays but longer than gamma rays.
Gamma rays- electromagnetic waves with the shortest wavelengths and highest frequencies
Transverse- moving or lying across something in a perpendicular way
Electromagnetic Waves are made up of vibrating electric and magnetic fields which move at the speed of light
Ex: Radio Waves, Microwaves, Infrared Rays, Visible Light, Ultraviolet Waves, and miniscule amounts of X-Rays and Gammas Rays
These are examples of electromagnetic waves that constantly surround us
The energy that is transferred through matter or space is called electromagnetic radiation
Radar is a technology which utilizes microwaves—a type of electromagnetic wave—which is used to detect objects in the atmosphere.
The U.S. Navy uses angular surfaces to reflect microwaves away from the radar source
Difference between electromagnetic and mechanical waves
Electromagnetic waves do not require a medium to travel through.
Electromagnetic waves can transfer energy through a vacuum
Mechanical waves do require a medium to travel through
Mechanical waves require a medium, such as air to travel
Mechanical waves are caused by a disturbance or vibration in a medium
Electromagnetic waves are caused by a source of electric and magnetic fields
These fields are produced by the movement of charged particles
Models of Electromagnetic Wave Behavior
Lights can either behave as a wave or a particle
Wave models explain most behaviors
Particle model for others
Light = electromagnetic wave (transverse wave)
Many properties of transverse, sometimes acts light a string or particles
Wave model of light
Wave model used to visualize light
Disturbance of charged particles makes a wave
Causes vibrating electric and magnetic fields
Perpendicular to each other
The 2 vibrating fields support each other and cause the energy to travel through a medium or space
A ray of light has these travellening disturbances
Vibrate in all directions
Polarizing filter: Acts like is has tiny horizontal or vertical slits
Light enters filter only vibrating electric fields go to the same direction
Slits can pass through them
Polarized light is the light that passes through
Polarized sunglasses: block out lights waves so your eyes aren't exposed to a lot of radiation
The photoelectric effect is when electrons are knocked out of a material after light is shined on it
When a high-frequency light shines on metal, electrons are knocked out, but low-frequency lights don’t have the energy to do so.
In light waves, they have a thing called photons which are the fundamental particles of light.
A way to visualize them is by thinking of the light wave as a stream filled with tiny packets(these are the photons)
To make the effect occur, each photons need to carry enough energy to knock out electrons
There is also something called diffraction which is the way the light spreads after passing through a narrow slit
When it spreads out it creates a striped pattern of light and dark areas.
An example could be when water spreads after passing through a narrow tunnel
These are some of the things that model waves cannot show, only particle models can
Electromagnetic (EM) waves have similar properties like amplitude, frequency, wavelength, wave speed, and energy, similar to mechanical waves
All EM waves travel at the same speed when in a vacuum.
EM waves are sorted into categories (like radio waves, visible light, and X-rays) based on their specific wavelengths or frequencies.
Different types are useful for different applications—you can't substitute a radio wave for an X-ray.
Wavelength and frequency are inversely related → high frequency means short wavelength.
Frequency is directly related to energy: higher frequency waves have more energy.
Visible light is the specific range of wavelengths that the human eye can see.
Radio waves have much longer wavelengths (lower frequency/energy) than visible light.
X-rays have much shorter wavelengths (higher frequency/energy) than visible light.
The Electromagnetic Spectrum
The Electromagnetic Spectrum. This is the complete range of electromagnetic waves ordered by increasing frequency. It includes radio waves, microwaves, infrared rays, visible light, ultraviolet rays, X-rays, and gamma rays
Mobile phones rely specifically on radio waves for communication. A network of towers transmits, receives, and relays these signals to connect users to each other and the internet
Wavelength and frequency radiation
Radio waves have the longest wavelengths and lowest frequencies
Gamma rays have the shortest wavelengths and highest frequencies
Microwaves
Microwaves have a shorter wavelength but a higher frequency than radio waves. A system that uses Microwaves is a radar. Radars are used for detecting objects and measuring their speed and distance
An example of a Radar in use is called Radar guns, which are what police use to detect if someone is over the speed limit
Infrared Rays
Infrared rays have an even shorter wavelength than Microwaves, but a higher frequency. A use of Infrared rays would be used for thermogram pictures. Instead of a normal camera, it is based on temperature
An example of infrared waves would be turning on an oven, or whatever you feel like using, and feeling an invisible heat on your hand. That is Infrared radiation, or Infrared Rays
Visible Light
Visible light is something that a human eye can see. It is also an electromagnetic wave and it has a shorter wavelength and a higher frequency than infrared rays
UV rays - ultraviolet rays
UV rays are electromagnetic waves with wavelengths just shorter than those of visible light
UV rays have higher frequencies and carry more energy than visible light
To protect ourselves from these harmful rays, we use sunscreen
X rays are electromagnetic waves with wavelengths shorter than those of ultraviolet rays
Have high frequencies
Penetrate most matter
Carry more energy than UV rays
Dense matter (ex: bone) absorbs X rays
That's why X rays are used to make images of bones
Gamma rays
Have the shortest wavelength
Highest frequencies
Out of all electromagnetic waves, they have the highest energy
Have beneficial uses but can also be very dangerous
Ex: people can use gamma rays in radio surgery
Combination of 200 beams of gamma rays, leaving tumor cells to stop spreading and reproducing
Lesson 5 - Light Waves
Dec 5, 2025
Transparent : A type of material that transmits light without scattering it.
Translucent : A type of material that scatters light as it passes through.
Opaque : A type of material that reflects or absorbs all of the light that strikes it.
Diffuse Reflection : Reflection that occurs when parallel light rays hit an uneven surface and all reflect at different angles.
Convex : A mirror that curves outward or lens that is thicker in the center than at the edges
Focal point - the point at which light rays parallel to the optical axis meet, after being reflected (or refracted) by a mirror (or lens)
Concave - a mirror with a surface that curves inward or a lens that is thinner at the center than at the edges
Compare - to tell the ways in which two or more things are alike and/or different
Light: Visible spectrum of color to humans
Light interacts with how we see the world around us
Materials can be classified by how much lights go through them
Classifications: Transparent, Translucent, Opaque
A material that lets the most light through is called Transparent
Ex: Glass, Window, Water
Completely see through-Transparent
A material that lets some light pass through but not all is called a Translucent material
Ex: Waxed paper, Gelatin deserts, Tinted windows
Somewhat see through- Translucent
A material that lets no light pass through it is called a Opaque object
Ex: Books, Hippopotamus, Marshmellow
No light passes through- Opaque
White light is a mixture of all colors in the rainbow. When white light shines on an object, some colors are reflected and others absorbed.
The color of an opaque object is the color of light it reflects.
Soccer ball example: reflects blue and red, absorbs others.
Brown tree trunk: reflects red + green (brown is a mix).
Black objects absorb all colors.
White objects reflect all colors.
Transparent/translucent objects: color is the light that passes through.
Example: green glass passes only green light.
Snow appears white because it reflects all colors.
If an object absorbs all light, it appears black
When white light shines on an object, and some of the colors of light are reflected and absorbed.
The color of an opaque object is the color of light that the object reflects
Black objects - absorbs all colors of light
White object - reflects all light
The color of a transparent or a translucent object is the color of light that passes through it
Ex: the color of clear, green drinking glass is green because the green light is the color that passes through the glass
Color of an object looks different than when white light shines on the object
Color of the light might come from white light shining through a colored filter or a thinted piece of glass or plastic
Red filter - transmits red light only
As light shines through a red filter, the part of the object that the light shines through looks red
Any other color - looks black
Ex: Color filters are used in photography and movies
Part of the special effects that help create different moods
Colored light changes how objects appear compared to white light. Filters are tinted glass/plastic that transmit only certain colors.
Red filter: transmits only red light.
Red parts of an object look red.
Other colors look black.
Filters affect how white light interacts with objects.
Used in photography/movies to highlight colors or create dramatic moods.
Light can reflect as well as transmit. Reflection occurs when parallel rays bounce off a surface.
Regular reflection:
Rays hit a smooth surface and reflect at the same angle.
Produces clear images (e.g., trees in still water).
Diffuse reflection:
Rays hit uneven surfaces, reflected at different angles.
Produces distorted or no image (e.g., choppy water).
Still water –> regular reflection –> clear image.
Choppy water –> diffuse reflection –> no image
Mirrors form clear images using reflected light. Three types: plane, convex, concave.
Plane mirror:
Flat surface.
Forms virtual image (appears behind mirror).
Upright, same size, but reversed left-right.
Convex mirror:
Curves outward (like outside of a bowl).
Forms smaller images.
The optical axis divides the mirror; the focal point is where parallel rays meet.
Concave mirrors curve inward (like the inside of a bowl)
Focal point is on the reflecting side.
Image depends on object’s position:
Object farther than focal point –> rays cross –> inverted real image.
Object between focal point and mirror –> upright, larger virtual image.
Inverted image = real image.
Light refracts (bends) as well as reflects. Lens = curved transparent material that refracts light.
Convex lens: thicker in middle, thinner at edges.
Light refracts toward the center; more curvature = more bending.
Convex lens can form virtual or real images:
Object between lens & focal point –> virtual, larger image (magnifying glass).
Object farther than focal point –> real image (size varies).
Convex lenses and concave mirrors both focus light; image type depends on object’s position relative to focal point.
Concave lens: thinner at center, thicker at edges. Light rays bend away from the optical axis.
Rays never meet –> only virtual images.
Images are upright and smaller than objects.
Comparison:
Convex lens and concave mirror both focus light.
Convex lens refracts light; concave mirror reflects light
Difference between Convex and Concave Lens:
Convex lens - a convex lens is thicker in the middle and thinner at the edges. It bends (refracts) light rays towards the center, which means that the rays meet at a focal point (focal point: where they meet/appear to meet). The images are always upright, virtual, and larger.
Ex: magnifying glasses, cameras, microscopes
Concave lens - a concave lens is thinner in the middle and thicker at the edges. It bends the light rays away from the optical axis, which means that the rays never meet. The images are always virtual, upright, and smaller than the actual object.
Ex: eyeglasses for nearsightedness
Difference Between Convex and Concave Mirrors
Convex - a convex mirror curves outward, like the outside of a bowl. It reflects the light rays outward, so that they appear to come from a focal point behind the mirror. They are always virtual, upright, and smaller.
Concave - a concave mirror curves inward, like the inside of a bowl. It reflects the light rays inward to meet at a focal point in front of the mirror. If the object is beyond focal point, it is real and inverted. If the object is between focal point and mirror, the image is virtual, probably upright or magnified.
TIP TO REMEMBER:
Convex - outward curve. Concave - inward curve
Lens - refracts. Mirror - reflects
Difference between regular and diffuse reflection
Regular reflection happens on a smooth surface (like a mirror). The light rays bounce off in the same direction, so you get a clear image.
Diffuse reflection happens on a rough surface (like paper or wood). The rays scatter in many directions, so no clear image forms.