Name: _________________________________ Date: ___________________________________
Reflection – Notes
“It’s like you’re my mirror, my mirror staring back at me …” – Justin Timberlake
When light hits certain surfaces, such as a mirror, it doesn’t get absorbed
– instead, it reflects. In your own words, write the definition of the word
reflection: Reflection is the process in which a surface bounces back the
light that hits it, without absorbing any of this light (i.e. when light bounces
off of a surface.
When light strikes (hits) a reflecting surface, it bounces off the surface,
and different types of rays are formed.
1. Incident Ray - A light ray that strikes (hits) a surface.
2. Reflected Ray - The light that is reflected from a surface.
To find out in which direction each ray of light is travelling, you can
measure an angle. To do this, draw a line is 90° (perpendicular) to the
reflecting surface EXACTLY where the incident ray hits it. This line is called
the normal. From here, two angles are created.
1. Angle of Incidence (i) – The angle between the incident ray and
the normal.
2. Angle of Reflection (r) – The angle between the normal and the
reflected ray.
Reflective Surface (Mirror)
r
i
Angle of
Reflection
Angle of
Incidence
Normal
The Laws of Reflection
1. The first law of reflection states: the angle of reflection (r)
is EQUAL to the angle of incidence (i).
2. The second law of reflection states that the incident ray, the
normal, and the reflected ray are all in the SAME PLANE (an
imaginary flat surface). This is why you can draw all three lines
on the same flat sheet of paper!
Mirrors can trick your brain. Light is reflected off of an object toward the mirror,
which reflects the light back to you. The object looks like it is located at the
point from where the light comes – a point behind the mirror’s surface. The
image appears to be the same size and shape as the real object, and it seems
to be the same distance behind the mirror as the real object is in front.
A smooth, flat reflecting surface always produces an image that has the
same size and same shape as the object.
When light reflects off a rough surface, diffuse reflection occurs and a
clear image no longer results, because the light is bounced in all different
directions.