How is Light Reflected?
Incident Ray
Reflecting Ray
Normal is the line perpendicular to the reflecting surface
Complete Reflection Activity
Based on this what do you believe the Law of
Reflection states?
normal is the line perpendicular to the reflecting surface
The Law of Reflection states that:
the angle of reflection = the angle of incidence
mirror
You can use a protractor to measure the angle of
incidence for an incident ray, and the angle of
reflection of for a reflected ray.
• the angle of reflection will be different
depending on if the surface is smooth or
rough
Light reflects
evenly, at an
opposite angle.
Light reflects in
a scattered
pattern.
How does a mirror work?
• light shines on an object… and
light is reflected from the object
• reflected light hits the mirror…
and are reflected back
– according to the law of reflection
• rays of light (image) that reach
your eye APPEAR to be
coming from behind the mirror
– because your brain believes light
travels in straight lines and so it
concludes (and tells you) the
object is behind the mirror
Why are the letters written
forwards & backwards?
What is
Refraction?
• the speed a ray of light travels depends on the
substance it is traveling through
– every substance has a refractive index which is a measure
of how fast a ray of light will travel through it
• when the ray of light changes substances its speed of
travel changes
• therefore the ray of light seems to bend
• the rays of light travel
through air faster than
water
• that’s because there are
more particles in the
water to slow it down
• so the pencil appears
broken at the point the
light rays change from
water to air
• the starting ray of light (in the 1st substance) is called the
incident ray
• the ray of light in the 2nd substance is called the refracted
ray
Law of Refraction
• when light travels from a less
dense substance to a more
dense substance (e.g. from air
to water) it will bend TOWARD
the normal line
• when light travels from a
denser substance to a less
dense substance (e.g. from
water to air) the ray will bend
away from the normal line
bends away from normal
bends toward normal
• looking from
above the
straw looks
broken and as
if one piece is
shifted
sideways
• that is because
of “optics”
Optics and Refraction
• when we see a ray of light coming towards us we
believe it is traveling in a straight line (instead of being
bent)
• so we imaging the object as being in a straight line from
our eye
• that’s why objects appear at a different place then we
think in a pail of water