Refraction & Reflection
Curriculum based on Secondary
students
Aim
• To learn how surfaces refract and reflect the
ray of light .
• The application and uses of refraction and
reflection in everyday life.
Objective
• Students should be able to understand and
apply the terms outlined and the nature of
reflection and refraction of light.
• Students should be able to use a ray model to
describe the behaviour of light.
Terms which should be known
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Incident Ray
Refracted Ray / Reflected ray
Laws of Refraction / Laws of Reflection
Critical Angle & Refractive Index
Real Image
Virtual Image
Concave/Convex (Focal length)
Incident Ray
• Is a ray of light that
strikes a surface. The
angle between this ray
and the perpendicular
or normal to the surface
is the angle of
incidence.
Reflective and Refractive Ray
Refracted Ray
• Is a ray of light that passes through a surface
to create the image. The angle between this
ray and the perpendicular or normal to the
surface is the angle of refraction.
Reflected Ray
• Is the ray of light that is reflected by the
surface.
• The angle between the incident ray and the
normal is the same as the angle between the
normal and reflected ray.
Laws of Refraction
1. (Snell's Law) Sin i/sin r is constant. This
constant is known as the refractive index of
the medium, and is denoted by n.
2. The incident ray, the normal and the
refracted ray are all on the same plane.
Laws of Reflection
1. The angle of incidence is equal to the angle
of reflection.
2. The incident ray, the normal and the
reflected ray all lie in the same plane.
Critical Angle & Refractive Index
The usual value of refractive index refers to
light going from air to a substance. If the
direction of the light ray is reversed, then i and
r are interchanged, and the refractive index
becomes the reciprocal of the conventional
value, e.g., If ang is 1.5, then gna is 1/1.5 =
0.67. These reciprocal vales are needed for
deducing the relationship between refractive
index (n) and critical angle (c), which is: c = sin
-1 (1/n)
Real Image
• Is an image in which the outgoing rays from a
point on the object pass through a single
point.
Virtual Image
• Is an image in which the outgoing rays from a
point on the object always intersect at a point.
Concave/Convex (Focal length)
• It is important to be able to draw ray diagrams
showing the formation of images by lenses and
mirrors and to be able to calculate values of
unknowns, using 1/p + 1/q = 1/f and
f1/p + f2/q = 1
• Concave: reflectors in torches; spotlights &
projectors; dentists' mirrors and shaving mirrors.
• Convex: gives a wide field of view in
supermarkets and inside buses.
Rationale
• Different teaching methodologies we have
obtained.
• Investigative approach (hands on).
• Engaging the students in every lesson because
science is interesting.
• Essentialism, Progressivism and Reconstructivism
are the philosophical ideas we will use when
teaching.
• Combining ICT with the lessons as a natural way
of learning.
The use of ICT
• Use the internet as one example of ICT in the
class – students research the refractive index
of different materials
• Use data projector and laptop or smart board
to play the following song which explains
reflection and refraction and the uses of each
• http://www.haverford.edu/physics/songs/snel
l.htm
Relating to real life.
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Telescopes
Opticians
Microscope
Cameras
Projectors
...the list can go on and on...