Mechanical Waves
What do all mechanical waves carry?
energy
What does it mean for two waves to be “in phase”?
Their crests and frequencies align at the same points in their oscillation.
What is sound?
A mechanical wave of vibrating particles creating pressure variations.
How are all electromagnetic waves similar?
All are transverse waves made of oscillating electric and magnetic fields.
How do light rays travel?
In straight lines until they hit a new medium or obstacle.
How do waves pass energy through a medium?
Vibrating particles transfer energy to neighboring particles.
What does the principle of superposition say?
The total displacement is the sum of the individual wave displacements.Waves lined up add and those not lined up subtract.
What causes a sonic boom?
A jet travels faster than the speed of sound, causing a shock wave.
Which electromagnetic waves have the shortest wavelengths?
X-rays, and gamma rays.
What is the difference between an incident ray, a reflected ray, and a refracted ray?
Incident → incoming ray
Reflected → ray that bounces off
Refracted → ray bent entering new medium
Why do waves eventually dissipate?
Particles stop vibrating and return to their original positions.
What is the difference between constructive and destructive interference?
• Constructive increases amplitude.
• Destructive decreases amplitude.
What does the speed of sound depend on?
Temperature and type of medium.
What do X-rays do to gases that allows photographic plates to change?
They ionize gases, causing chemical changes.
Why does a smooth surface produce a clear reflection while a rough one produces a diffuse reflection?
Smooth surfaces reflect rays in the same direction; rough surfaces scatter them.
What is the difference between transverse and longitudinal waves?
• Transverse: particles vibrate at right angles to the wave direction.
• Longitudinal: particles vibrate in the same direction the wave travels.
What is a node, and what is an antinode?
Node → point of continuous destructive interference (no movement)
Antinode → point of constructive interference (maximum movement)
How do ultrasound and sonar work?
They send sound waves into a medium and detect echoes to form images.
What is the difference between phosphorescence and fluorescence?
• Phosphorescence: caused by gamma or X-rays, continues glowing after exposure.
• Fluorescence: caused by UV light, glows only when exposed.
Explain how iridescence creates shimmering colors.
Light rays interfere after being refracted at different angles, strengthening some colors and weakening others.
Name three ways a wave can be measured and what each measurement represents.
Amplitude → height or energy of the wave
Frequency → number of waves per second
Wavelength → distance between crests (or compressions)
Explain how a standing wave forms and why it appears not to move.
A standing wave forms when two waves of the same frequency move in opposite directions; their interference creates fixed nodes and antinodes, making the wave appear stationary.
What is the Doppler effect, and why does pitch change when a sound source moves?
The Doppler effect is a change in frequency heard when the source or listener moves. Waves compress when approaching (higher pitch) and stretch when moving away (lower pitch).
Compare long-wavelength EM waves and short-wavelength EM waves in terms of energy and uses.
Long wavelengths (radio, infrared): low energy; used for communication & heat sensing.
Short wavelengths (UV, X-ray, gamma): high energy; used to sterilize, image, or treat diseases.
A superhero named WaveRider can choose one special power:
• Control transverse waves,
• Control longitudinal waves, or
• Control electromagnetic waves.
Based on what each type of wave can do in real life, which power would be the MOST useful for saving people, and why?
(Explain using actual wave behavior from what you learned.)
Electromagnetic waves