Module 3 : Waves Flashcards
(Waves Part 1 : Basic Characteristics of Waves)
What is a wave?
- a disturbance that travels through space and time accompanied by the transfer of energy
- it is a vibration, a vibration is a wiggle, and a wiggle that travels is called a wave
- carry energy from one place to another
(Waves Part 1 : Basic Characteristics of Waves)
Explain the difference between a transverse wave and a longitudinal wave, and give examples of each
- Transverse wave : moves up and down, perpendicular (examples : water waves, electromagnetic waves, and light waves)
- Longitudinal wave : moves from left to right, parallel to one another (example : sound waves, tuning fork, earthquake seismic waves)
(Waves Part 1 : Basic Characteristics of Waves)
Describe the following terms associated with waves :
(A) wavelength
(B) frequency
(C) amplitude
(A) wavelength :
- property of a wave that is the distance between identical points in between two successive waves
- the distance between one crest (or trough) of one wave and the next is considered wavelength
(B) frequency (often measured in hertz Hz) :
- the number of to and fro vibrations made in a given time (usually one second)
- how many waves pass by per unit of time
(C) amplitude :
- same thing as height
- measurement of wave from the center, or equilibrium point to the highest point (top of peak)
- in astronomy, it tells you about the intensity of something
(Waves Part 1 : Basic Characteristics of Waves)
amplitude
- the maximum displacement on either side of the equilibrium (midpoint) position
(Waves Part 1 : Basic Characteristics of Waves)
frequency
- the number of vibrations per unit time
- for a wave, the number of crests that pass a particular point per unit time
(Waves Part 1 : Basic Characteristics of Waves)
period
- time required for a vibration or a wave to make a complete cycle, equal to 1/frequency
(Waves Part 1 : Basic Characteristics of Waves)
wavelength
- the distance between successive crests, troughs, or identical parts of a wave
(Waves Part 2 : Reflection Refraction, Diffraction, and Interference)
Explain reflection, refraction, and diffraction of waves.
- reflection : the returning of a wave to the medium from which it came when it hits a barrier
- refraction : the path of a wave bends due to moving from one medium to another
- diffraction : spreading of two or more waves with each other
(Waves Part 2 : Reflection Refraction, Diffraction, and Interference)
What is interference? How do constructive and destructive interference differ?
- interference : the interaction of two or more waves with each other
- constructive interference : when two identical waves overlap each other at the crest, result is wave with increased amplitude (example : in a concert hall, hearing two speakers and getting a “loud” spot)
- destructive interference : when crest of one wave and trough of another wave overlap, effect is reduced, high part fills in low part and they cancel each other out (example : noise cancelling headphones)
(Waves Part 3 : The Doppler Effect)
What is the Doppler effect?
- the change in frequency of a wave due to the motion of the source (or due to the motion of the receiver)
- blue shift : light moving towards you, shorter frequency
- red shift : light moving away from you, longer frequency
(Waves Part 3 : The Doppler Effect) A train travels towards you, emitting a horn at a frequency of 256 Hz. Due to the Doppler Effect, the frequency of sound that you hear is actually : (A) higher than 256 Hz (B) lower than 256 Hz (C) equal to 256 Hz
ANSWER
(A) higher than 256 Hz
(Waves Part 4 : Sound vs Light)
What changes the pitch of sound?
- the speed of vibrations
- low pitch = low frequency = lower vibrations
- high pitch = high frequency = higher vibrations
(Waves Part 4 : Sound vs. Light) Sound travels fastest in : (A) air (B) water (C) steel (D) a vacuum (nothing at all)
ANSWER
(A) steel
(Waves Part 4 : Sound vs. Light)
Light requires a medium to move through.
True or false?
ANSWER
false
(Waves Part 4 : Sound vs. Light) Which of the following is NOT a transverse wave? (A) sound (B) light (C) water (D) "the wave" at a stadium
ANSWER
(A) sound
(Electromagnetic Spectrum)
What is an electromagnetic wave?
- also known as light
- accelerating electric charge : creates an oscillating electromagnetic field
- transverse waves
- requires no medium
- all travel at the same speed 300,000,000 m/s
(Electromagnetic Spectrum)
List the types of electromagnetic waves that are located on the electromagnetic spectrum in order from highest frequency to lowest frequency.
(A) gamma rays : used to treat; diagnose cancer (highest energy wave, tiny short waves, high frequency - emits red light)
(B) x-rays : used to detect broken bones; detects cavities in teeth
(C) ultraviolet rays : are used to sanitize because they have the ability to kill bacteria; whitens teeth
(D) visible light : middle of the electromagnetic spectrum - this is what we see as visible light
(E) infrared : thermal imaging; detects heat
(F) microwaves : used to heat food
(G) radio waves : wireless internet; cell phones (longest wavelength, low frequency, low energy. Used in communications)
(Electromagnetic Spectrum)
How are electromagnetic waves the same? How do they differ?
- same : they all travel at the same speed
- different : some we can see and others we can’t (we can only see the ones beyond visible light, but not the ones before it), they also differ in intensity and wavelength