Waves Flashcards
(14 cards)
What is a wave?
A wave is a transfer of energy without the net transfer of matter.
What are the two main types of waves?
Transverse waves: oscillations are perpendicular to the direction of energy transfer
Longitudinal waves: oscillations are parallel to the direction of energy transfer
Define the following wave terms: amplitude, wavelength, frequency, period, wave speed.
• Amplitude: maximum displacement from rest position
• Wavelength (λ): distance between two corresponding points on a wave (e.g. peak to peak)
• Frequency (f): number of waves passing a point per second (Hz)
• Period (T): time for one wave to pass a point
• Wave speed (v): speed at which energy is transferred
What is a longitudinal wave made of?
• Compressions: regions where particles are close together
• Rarefactions: regions where particles are spread apart
What is the difference between mechanical and electromagnetic waves?
• Mechanical waves need a medium (e.g. sound).
• Electromagnetic waves do not require a medium and can travel through a vacuum (e.g. light, radio).
What is the electromagnetic spectrum?
increasing frequency (or decreasing wavelength):
Radio → Microwaves → Infrared → Visible → Ultraviolet → X-rays → Gamma rays.
What are the common properties of all EM waves?
• They are transverse
• Travel at the same speed in a vacuum (3 × 10⁸ m/s)
• Transfer energy
• Can be reflected, refracted, and diffracted
What is refraction? Why does it happen?
Refraction is the bending of waves when they pass from one medium into another due to a change in wave speed.
What happens to wave direction during refraction when entering a denser medium?
The wave slows down and bends towards the normal.
What happens to wave direction during refraction when entering a less dense medium?
The wave speeds up and bends away from the normal.
How can you measure the speed of sound in air?
Use an oscilloscope to measure time between pulses and a known distance between microphones, then apply v =d/t
How do you determine the wavelength of a wave on a string or water surface?
Use a strobe light or ruler to measure the distance of several waves, then divide by the number of waves.
What is ultrasound?
Sound waves with frequencies above 20,000 Hz — above the human hearing range.
How is ultrasound used in medicine and industry?
• Medicine: prenatal scans and detecting kidney stones
• Industry: detecting flaws in materials (cracks)
