Unit 3 Flashcards
wave speed formula
frequency x wavelength
features of transverse waves
has peaks and troughs
vibrations are at right angles ot the direction of propogation
features of longitudinal waves
consists of compressions and rarefactions
vibrations are parallel to the direction of propogation
what is a wavefront
a surface containing points affected in the same way by a wave at a given time
what is reflection
when a wave bounces off a boundary
what is refraction
a wave moves from one medium to the other
what is diffraction
a wave spreads as it moves through a gap
what happens when a wave moves through a new medium
speed and wavelength will change
what happens when a wave passes through a gap
wave spreads outwards from the gap in a curved pattern
what images do all mirrors create and what features do they possess
virtual images
they are the same size and distance from the mirror
upright
what is a virtual image
image that cant be displayed on screens
what is a real image
can be projected onto a screen because light actually passes through
what happens when light moves to a denser medium(air to glass)
light will slow down and change direction towards the normal
what happens when light moves to a rarer medium(glass to air)
it will speed up and move away from the normal
what happens when light enters at the normal
there is a change in speed but not change in direction
what is refractive index and how is it calculated
measures how much the speed of light changes when it moves from a vacuum to a material
speed of light in vacuum/speed of light in medium = refractive index
what is snells law
sin i / sin r = refractive index
What happens when the angle of incidence is larger than the critical angle
Total Internal Reflection
light gets reflected back into the medium
only happens in denser to rarer
what is the critical angle and how is it found
the largest angle of incidence where light can escape the medium
n(refractive index) = 1/sinC
What is a converging lens
when light rays are brought towards the principle focus
what is a diverging lens
when light rays are spread out as if coming from the principle focus
What is the focal length
the distance between the centre of the lens and the principle focus
when are virtual images created
created when the object is inside the focal length and rays move backwards so the image cannot be created on a screen
when are real images created
when the object is outside the focal length
image created will be upside down and real
what can short sightedness be fixed with
by using a diverging lens
what can long sightedness be fixed with
by using a converging lens
why does a beam of white light disperse
because different colors travel at different speeds
what is light that only contains one frequency called
monochromatic light
order of colors in decreasing frequency
violet,indigo,blue,green,yellow,orange,red
what type of waves is the electromagnetic spectrum
transverse waves that do not require a medium
what speed do electromagnetic waves travel at
3 x 10^8 m/s
order of the spectrum in increasing frequency
radio waves,micro waves,infra red, ultraviolet, x-rays,gamma rays
what are radio waves used for
transmit television and radio signals
what are microwaves used for
similar to radio waves
able to penetrate the upper atmosphere
danger is heating effect
what is infra red used for
can be used for optic fibres
can be used for remote controls
can cause burns
what is visible light
just electromagnetic radiation that is visible
what is ultraviolet radiation used for
produced by sun
high amounts of UV can sterilise water and check for fake banknotes
can cause skin cancer and eye conditions
what are x rays
short wavelength rays
it can pass through materials easily but get absorbed by others
they can damage cells
what are gamma rays
they can kill cancer cells
can kill living cells and damage DNA
sterilise equipments
what type of waves is sound waves
they are longitudinal and made of compressions and rarefactions
do sound waves require medium
yes
what range can human ears hear
20 to 20,000 Hz
what are sounds above 20,000 Hz called
Ultrasound
what is an echo
when sound waves reflect when they encounter a boundary
