Unit 3 - Waves Flashcards
what is a wave
the transfer of energy and information but not matter in the form of vibrations
what are transverse waves
a wave where the vibrations are perpendicular to the direction of wave travel
what are longitudinal waves
a wave where the vibrations are parallel to the direction of wave travel
name any 2 transverse waves
light (including the electromagnetic spectrum), ripples on water
name any longitudinal wave
sound wave
define amplitude
maximum displacement of a material
define wave front
a line where all the water affected by a wave rises or falls together
define frequency
number of oscillations per unit time (Hz)
define wavelength
distance between 2 consecutive points on a wave (m)
define periodic times
the time for one complete oscillation, T
formulae for wave speed
wave speed = frequency x wavelength
v = f.λ
formulae for frequency
frequency = 1 / time period
f = 1 / T
doopler effect -
if a source of sound is getting closer observed frequency will be ——— and wavelength will be ———
if a source of sound is getting closer observed frequency will be higher and wavelength will be lower
doopler effect -
if a source of sound is getting further observed frequency will be ——— and wavelength will be ———
if a source of sound is getting further observed frequency will be lower and wavelength will be higher
the faster the source is moving , the (bigger / smaller ) the change in frequency
bigger
the frequency remains constant even if the wave changes medium. True or false
True
the wave speed never changes unless medium changes . True or False
True
What if wave changes medium ?
if the object is **more dense ** ,
longitudinal waves will ————- speed
increase
What if wave changes medium ?
if the object is **more dense ** ,
transverse waves will ————- speed
decrease
extra information - what are electromagnetic waves
a combination of electric and magnetic feild
state some properties of electromagnetic waves
- they have the same speed in free space/vacuum
- they can travel in vacuum
- they are all transverse
Name the waves of the electromagnetic spectrum in terms of increasing frequency and decreasing wave length.
Gamma
Xray
Ultraviolet
Visible light
Infrared
Microwave
Radio wave
Name the colors of visible light in terms of
VIBGYOR
Violet
Indigo
Blue
Green
Yellow
Orange
Red
State the use of the electromagnetic wave -
radio wave
- communication
- broadcasting
State the use of the electromagnetic wave -
microwave
- cooking
- satellite transmissions
State the use of the electromagnetic wave -
infrared wave
- heaters
- night vision equipment
State the use of the electromagnetic wave -
visible light
- optical fibers
- photography
State the use of the electromagnetic wave -
ultraviolet wave
fluorescent lamps
State the use of the electromagnetic wave -
x ray wave
- medical applications , observing internal structure
state the use of the electromagnetic wave - gamma ray
- sterilizing food and medical equipment
- kill cancerous cell
state the effects of excessive exposure to microwaves
internal heating of body tissues
state the effects of exposure of infrared rays
skin burns
state the effects of exposure of ultraviolet rays
damage to surface cells and blindness
state the effects of exposure of gamma rays
cell mutation
cancer
etxra - what do you mean by excessive exposure
exposure can mean exposure to high intensity/amplitude or exposure for a long time
state the law of reflection
angle of incidence = angle of reflection
i = r
what do you understand by refraction
change in direction , ‘bending’ happens when wave changes medium
when a wave goes to a denser medium , wave become (toward/away) from the normal
toward
when a wave goes to a less dense medium , wave become (toward/away) from the normal
away
extra - what do you mean by refractive index
the ratio of speed of light in air to the speed of light in a material . it has no units
refractive index is always greater than 1 . True or False
True
formulae to find refractive index
speed of light in vaccum / speed of light in medium
formulae to find refractive index
sin i / sin r
define critical angle
learn any 1 form these 2
- a critical angle of a material is the maximum angle of incidence for which there is any refraction above this value light will be relected within the material
- when light moves to a less dense medium, critical angle is the angle of incidence that results in an angle of refraction=90°
formulae to find refractive index
1/sin c
define total internal reflection
when light comes from a more dense medium with an angle greater than the critical angle , all the light will reflect back , reflection is inside the material
state some uses of total internal relfection
-endoscopes
-optical fibers for communication
optical fibers in decorative lamps
- in safety reflector
extra how do optical fibres work
they transfer data in the form of light theough series of total internal reflection
range of human audible sound
20 to 20,000 Hz
range for ultrasounds
above 20,000 Hz
what will increase if the frequency increase
pitch
what will increase if the amplitude increases
loudness
extra- what is echo location
calculating the distance by detecting the time it takes for a wave to reflect from a barier
divide time by 2
describe how the student could use the oscilloscope and microphone to determine the frequency of a sound
1) connect microphone to the oscilloscope
2) adjust the oscilloscope to give a minimum of one complete oscillation on the screen
3) measure the number of squares for a complete wave and multiply by time base
4) f = 1/T
what does an oscilloscope do
a device that will represent longitudinal waves as transverse waves.
wavelength is longer in (more dense / less dense ) medium
more dense
state the name of the process that seperates the colors in white light
dispersion of light
state the property of the glass of the prism that causes white light to be split into the different colors of the spectrum
transparent denser medium causes refraction of colors with different angles
state two uses of optical fibres
- to carry telephone signals
- for medical imaging
- specified lighting
