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
