waves unit review

Frequency

Number of wave cycles passing a point per second.

Period

Time required for one complete wave cycle to pass.

Transverse Wave

Wave where particles displace perpendicular to wave direction.

Longitudinal Wave

Wave where particles displace parallel to wave direction.

Surface Wave

Wave traveling along a boundary between two different media.

 Crest

Highest point of a transverse wave displacement.

Trough

Lowest point of a transverse wave displacement.

Rarefaction

Low-density region in a longitudinal wave.

Compression

High-density region in a longitudinal wave.

Amplitude

Maximum displacement of a particle from its rest position.

Constructive interference

Two matching waves combine to create a larger amplitude.

Destructive interference

Two opposing waves combine to decrease or cancel amplitude.

Standing waves

 A vibrational pattern created when two identical waves travel in opposite directions and interfere with each other.

Reflection

The bouncing back of a wave when it hits a surface or boundary that it cannot pass through. The angle of incidence always equals the angle of reflection.

Refraction

The bending of a wave as it passes from one medium into another. This bending is caused by a change in the wave's speed.

Diffraction

The bending, spreading, or stretching of waves as they move around the edge of an obstacle or pass through a narrow opening.

Doppler effect

The apparent change in the frequency or pitch of a wave caused by the relative motion between the wave source and the observer. The pitch sounds higher as the source approaches and lower as it moves away.

Resonance

The phenomenon that occurs when a wave or external force drives another system to oscillate with greater amplitude at a specific, preferential frequency (known as the system's natural frequency).

What type of wave is a sound wave?

Mechanical longitudinal wave

How are sound waves created?

Vibrating objects create compressions and rarefactions in air

What is pitch?

How humans perceive frequency

How does string length affect pitch?

Shorter = higher pitch, longer = lower pitch

How does string thickness affect pitch?

Thicker = lower pitch, thinner = higher pitch

How does tension affect pitch?

Tighter = higher pitch, looser = lower pitch

How do keys affect pitch on a flute?

Longer air column = lower pitch, shorter = higher pitch

What does blowing harder do?

Produces higher pitch (harmonics)

What does changing airstream angle do?

 Slightly changes pitch

Difference between mechanical & EM waves?

Mechanical need a medium; EM do not

How are EM waves created?

Accelerating charged particles

What is the EM spectrum?

All EM radiation types by wavelength/frequency

Can humans see all EM waves?

 No, only visible light

What cells detect light/color?

 Rods and cones

Why is color hard to see in low light?

 Cones need bright light; rods only see grayscale

How do we see many colors with 3 receptors?

Trichromatic vision

What happens when red + blue light mix?

Magenta

What happens when red + green light mix?

Yellow

What happens when blue + green light mix?

Cyan

 What happens when all light colors mix?

White

 How is pigment mixing different?

 It absorbs light → makes dark/muddy colors

What did Greek philosophers think about vision?

Eyes emit “visual fire”

What is Alhazen’s theory?

Intromission (light enters the eye)

What is the double-slit experiment?

Light creates interference pattern

What does it prove?

 Light behaves as a wave

What is the photoelectric effect?

 Light knocks electrons off metal

What does the photoelectric effect prove

Light behaves as particles (photons)

Why is “radiation” scary?

Association with nuclear disasters

What is ionizing radiation?

High energy, damages DNA

Examples of ionizing radiation?

UV, X-rays, gamma rays

What is non-ionizing radiation?

Low energy, only heats/vibrates molecules

Examples of non-ionizing radiation?

Radio, microwave, infrared, visible light