define refractive index
refractive index of a material is the ratio of how fast light travels through that particular substance to the speed of light in a vacuum.
what is a medium?
a transparent material
what is refaction?
-The change in direction of a wave when it passes through a boundary between mediums of different density.
-This change of direction is caused by a change in the speed of different parts of the wavefront as they hit the boundary.
what happens to a wavefront when it hits a boundary?
A wavefront changes direction when part of it hits a boundary and changes speed before the other parts.
what are the conditions for refraction?
-The more optically dense the medium, the slower the waves travel and the smaller the angle of refraction, The light bends towards the normal.
The amount of refraction that takes place is determined by the difference between the angle of incidence (i) and refraction (r) of the waves at the boundary.
what is the difference between angle of incidence and angle of refraction?
-angle of refraction is the one which enter a different density and angle of incidence is before it enters a difference refractive index.
what does the amount of refraction depend on?
-The amount of change in direction that takes place depends on the difference in optical density between the two media.
-when light passes from a less dense to more dense medium, the refracted light has a lower speed and a short wavelength than the incident light, frequency stays the same.
what happens when light passes from a less dense to a more dense material?
the ray refracts towards the normal
when a wave refracts what changes and what doesn’t change?
its speed and wavelength change but its frequency remains the same. This is noticeable by the facts that the colour of the wave doesn’t change.
snells law relates to?
change in different refractive index.
n1sin1 = n2 sin2
what is the critical angle?
90 degrees
-The larger the refractive index of a material, the smaller the critical angle
how does the angle of incidence and angle of refraction change when a light is shone between a denser and a less dense material?
-As the angle of incidence is increased, the angle of refraction also increases, until the angle of incidence reaches the critical angle.
When the critical angle is > angle of incidence
The ray is refracted along the boundary between in two materials.
when the angle of incidence > critical angle
total internal refraction occurs.
what is TIR?
-Total internal refraction a special case occurring when the angle of incidence within the denser medium is greater than the critical angle (90’)
-higher to a lower boundary (ex-fibre optics)
-lights with a higher refractive index are more likely to be totally internally reflected.
