P4+P11 Waves, Light and Sound Flashcards
what’s the relationship between ANGLE OF INCIDENCE and ANGLE OF REFLECTION?
equal
how do you measure the angle of REFLECTION?
the angle between the normal and the reflected ray
characteristics of REFLECTION (4)
same size
same distance
laterally inverted image
virtual image
explain what happens during REFRACTION
light enters a different medium → CHANGES SPEED → BENDS (at an angle of refraction)
when light enters a MORE DENSE medium…
slows down
bends towards the normal
when light enters a LESS DENSE medium…
speeds up
bends away from normal
define REFRACTIVE INDEX
a measure of how much a material SLOWS DOWN the light that passes through it
how do you calculate the refractive index? (2)
speed of light in air / speed of light in substance
= sin (angle in air) / sin (angle in substance)
what is TOTAL INTERNAL REFLECTION?
what is the condition for it to occur?
when ALL LIGHT REFLECT and NONE REFRACT;
it occurs when angle of incidence beyond critical angle
what is the CRITICAL ANGLE?
the angle beyond which total internal reflection occurs
what are OPTICAL FIBERS? what does the diagram look like?
angle of incidence > critical angle → light always internally reflects
check diagram in notes:)
uses of OPTICAL FIBERS
- periscope for communication
* endoscope for medicine
what are CONVEX LENSES?
converging lenses
what is the FOCAL POINT in convex lenses?
where the rays meet
what is the FOCAL LENGTH in convex lenses?
distance between center of the lens and focal point
how do you draw RAY DIAGRAMS?
1st ray: parallel to principal axis until center, through focal point
2nd ray: through the center
example of a REAL+DIMINISHED image
camera
eyes
example of a REAL+ENLARGED image
projector
example of a VIRTUAL+ENLARGED image
magnifying glass
what’s the difference between REAL and VIRTUAL image?
real can be projected onto a screen; virtual cannot
properties of all ELECTROMAGNETIC WAVES
- transverse
- don’t require particles to travel
- same speed of 3x10^8 m/s
state all types of ELECTROMAGNETIC WAVES
in the order of wave energy, from least to most
radio - micro - infrared - visible light - uv - xray - gamma
use of RADIOWAVE
broadcast
radar
use of MICROWAVE
microwave oven/satellite/mobile phone communication
use of INFRARED RADIATION
thermal imaging (medical disgnosis, intruder alarm, etc.) remote controls
use of VISIBLE LIGHT
sensation of sight
optical fiber
use of UV
disinfection
use of X-RAY
x-ray pictures
checking banned materials
use of GAMMA RAY
cancer treatments
danger of MICROWAVE
could cause burns inside body
danger of UV
sunburn
skin cancer
danger of X-RAY
over-exposure damages cells
danger of GAMMA RAY
kills living cells
damages DNA
what is one way of PROTECTION against X-RAYS?
protective suit made of LEAD (absorbs x-rays)
what do waves transfer?
what do waves not tranfer?
waves transfer ENERGY; not matter
define a WAVE (2)
oscillation/vibration (1) transfers energy (1)
explain the difference between TRANSVERSE and LONGITUDINAL waves
T: direction ofvibration PERPENDICULAR to directionof energy transfer
L: direction ofvibration is PARALLEL to directionof energy transfer
draw a diagram of TRANSVERSE WAVE, label all important parts
check notes:)
draw a diagram of LONGITUDINAL WAVE, label all important parts
check notes:)
T: how do you measure WAVELENGTH?
distance from crest to crest/trough to trough
T: how do you measure AMPLITUDE?
from equilibrium to crest/trough
L: how do you measure WAVELENGTH?
distance between successive compressions/rarefactions
L:
what are COMPRESSIONS? what are RAREFACTIONS?
C: high particle density → high pressure
R: low particle density → low pressure
examples of TRANSVERSE waves
light, water, slinky
examples of LONGITUDINAL waves
sound, slinky
what is FREQUENCY?
what unit is it measured in?
number of oscillations in 1s / complete waves passing a given point in 1s
hertz (Hz)
what is WAVE SPEED? what unit is it measured in?
distance moved by the wave in 1s
m/s
what’s the equation for wave speed, frequency and wavelength?
wave speed = frequency • wavelength
v = f • λ
draw CIRCULAR WAVES
label the wavefronts + direction of wave spreading
circular wavefronts + wave spreads in all directions + wavefront perpendicular to direction that wave spreads
*check diagram in notes!
draw PLANE WAVES
label the wavefronts + direction of wave spreading
vertical+parallel wavefronts + wave spreads horizontally + wavefront perpendicular to direction that wave spreads
*check diagram in notes!
define REFLECTION in terms of waves
as waves bounce off a surface, they CHANGE DIRECTION
does wave speed change in REFLECTION?
no
define REFRACTION in terms of waves
as waves pass through a different medium, they CHANGE SPEED + DIRECTION
define DIFFRACTION in terms of waves
as waves pass through a GAP, they SPREAD outwards
draw a diagram for REFLECTION, label the wavefronts
check notes:)
draw a diagram for REFRACTION, label the wavefronts
check notes:)
draw a diagram for DIFFRACTION, label the wavefronts
check notes:)
what type of waves are SOUND waves? can it travel in vacuum?
longitudinal; no
what type of waves are LIGHT waves? can it travel in vacuum?
transverse; yes
what’s the SPEED OF SOUND in air?
330 m/s
what’s the SPEED OF LIGHT?
always 3x10^8 m/s
what makes a sound LOUDER?
LARGER vibration → increased AMPLITUDE → increased loudness
what makes a sound HIGHER PITCHED?
FASTER vibration → increased FREQUENCY → increased pitch
what is the range of human hearing?
20 Hz - 20,000 Hz
what are INFRASOUND and ULTRASOUND? what are their uses?
INFRASOUND: too LOW frequency for human to hear → detect earthquake
ULTRASOUND: too HIGH frequency for human to hear → sonar, ultrasonic scans
draw a diagram for REFLECTION OF LIGHT, label the rays + normal + angles
check notes:)
draw a diagram for REFRACTION OF LIGHT, label the rays + normal + angles
check notes:)
