P3 waves Flashcards
what do waves transfer
energy, WITHOUT transferring matter
describe transverse wave
direction of vibration at right angle to direction of propagation
examples of transverse waves
- electromagnetic radiation
- water waves
- seismic S-waves
describe longitudinal wave
direction of vibration is parallel to direction of propagation
examples of longitudinal waves
- sound waves
- seismic P-waves
features of a wave
- wavelength
- frequency
- crest (peak)
- trough
- amplitude
- wave speed
equation for wave speed
what causes the refraction of waves in water
depth change
what causes refraction of wave
change in speed
how does water wave passing over shallower region change it
- slow down
- wavelength decrease
what causes diffraction
wave passes thru gap
when is diffraction more pronounced
when size of gap and wavelength similar
impact of wavelength on diffraction
longer wavelengths diffract more
impact of size of gap on diffraction
smaller gap means more diffraction
where is angle of incidence/reflection measured from?
normal
Characteristics of an optical image by a plane mirror
- same size
- same distance from mirror
- laterally inverted
characteristics of image
- enlarged / same size / diminished
- upright / inverted
- real / virtual
Relationship between angle of incidence and angle of reflection
Equal
Define refraction
- change in direction of a light ray
- passing from one medium to another
Define refraction
- change in direction of a light ray
- passing from one medium to another
Define refractive index
Ratio of speeds of wave in 2 diff regions
Equation for refractive index
Speed of light in substance / speed of light in vacuum
What happens when light enters medium with higher refractive index
Bend toward normal
What happens when light enters medium with higher refractive index
Bend toward normal
Define critical angle
- angle of incidence
- at which angle of refraction is 90 degrees and above
- which all light is totally internally reflected
Uses for total internal reflection
- endoscope (medicine)
- optical fibre for communication
What happens to image inside focal length of converging lens
- enlarged
- virtual
- upright
What happens to image inside focal length of converging lens
- enlarged
- virtual
- upright
What happens to image outside focal length of converging lens
- diminished
- inverted
- real
What happens to image at principal focus of converging lens
No image formed
Colours of visible spectrum in order of frequency (low to high)
Order of wavelength (low to high)
red orange yellow green blue indigo violet
violet indigo blue green yellow orange red
Which light is bent most in a prism and why
Violet as it has the greatest changes in speed
Main regions of EM spectrum in order of frequency (low to high)
In order of wavelength (short to long)
radio, microwave, infrared, visible, ultraviolet, x-ray, gamma
gamma, x-ray, ultraviolet, visible, infrared, microwave, radio
Speed of EM waves in vacuum vs air
3.0*10^8 m/s
Approx same in air
Applications of radio waves
- radio and television transmissions
- radar
Applications of microwaves
- satellite television
- mobile (cell) phone
- microwave ovens
Applications of infrared
- remote controllers for televisions
- thermal imaging
Applications of visible light
- vision
- photography
Applications of ultraviolet
- detecting fake bank notes
Applications of x-rays
- medical scanning
- security scanners
Applications of gamma rays
- detection of cancer
- treatment of cancer
Harmful effects of excessive exposure to ultraviolet radiation
- damage to surface cells and eyes
- leads to skin cancer and eye conditions
Describe harmful effects of x-rays and gamma rays
- mutation or damage to cells in body
How is sound produced
Vibrating sources
Describe the longitudinal nature of sound waves in air
Series of compressions and rarefractions
Describe what is meant by compressions
Regions of higher pressure due to particles being closer together
Describe what is meant by rarefractions
Regions of lower pressure due to particles being spread further apart
Is medium needed to transmit sound waves?
Yes
Method for determining speed of sound in air
- Measure large distance in straight line. Two people stand this distance apart
- First person produces loud noise at same time as making visible action
- Second person starts stopwatch when see first person move, stop stopwatch when hear sound
Relative speeds of sound in states of matter in order of decreasing speed
Solids, liquids, gases
How does amplitude affect sound
Changes loudness
How does change in frequency affect sound waves
Pitch
Describe what is meant by an echo
The reflection of a sound wave
Define ultrasound
Sound with a frequency higher than 20kHz
