Light and Sound (Reflection/Refraction/TIR) Flashcards
what does ‘i’ stand for
angle of incidence
what does ‘r’ stand for in reflection?
angle of reflections
what does the law of reflections say?
i=r
how can we see?
light from the sun and light bulbs reflect off every surface
what happens when i=0?
the light doesn’t change direction
define refraction
the change in direction of a wave as it changes speed
define reflection
the return of light or sound waves from a surface
what is the normal?
a dotted line drawn perpendicular to the surface of the refracting material
what is a wavefront?
lines along the crest of a wave
rays and wavefronts are always at what angle?
90 degrees
reflection does not change the…
wavelength (lambda)
in deep water waves travel… but in shallow water they travel…
faster - slower
if i=0…
there is no change in direction
if i=/ 0…
water waves refract towards the normal
what does ‘r’ stand for in refraction?
angle of refraction
when does wavelength always change?
in refraction
why does the ray change direction in the water?
one side (X) slows down before the other side (Y) (a bit like slowing the left-hand side of a sledge and using the left foot causing it to turn left)
refraction doesn’t change the…
frequency
what is one thing that doesn’t change in refraction?
the frequency
lenses are found in:
cameras, eyes, telescopes, microscopes
what is the wave equation?
v = f * λ
how does light travel?
in a straight line
what is an example of refraction?
shallow writing- writing appears to be higher
in these optical illusions causes by refraction…
- light speeds up as it leaves the water/glass
- it refracts from the normal
- its assumes light travels in a straight line so we see a virtual image
what does TIR stand for?
Total Internal Reflection
when does TIR happen?
- moving from a slow medium to a fast-medium
2. when the angle of incidence is greater than the critical angle (i>c)
what is a medium?
a substance or material that carries the wave
what is the critical angle?
the angle of incidence is called the critical angle
what is a fast-medium?
air/vacuum
does the critical angle change?
the critical angle varies depending to the material used
how does TIR work?
when the ray is greater than the critical angle, the ray will reflect
but if the ray is less the critical angle, the ray will refract through the medium ( i=r ; angle of incidence and reflection are the same)
what is the critical angle for glass?
42 degrees
TIR happens when…
i = r
where is the normal?
90 degrees from the medium’s line
name 3 examples TIR can be found in
- a periscope
- bike reflector
- communication cables around the world
