Reflections
Aims: to explore reflections and the concept of an image.
NC links:
Sc4 that light is reflected from surfaces [ for example,
mirrors, polished metals ]
Equipment
for students
 flat mirror
 curved mirror
 flexible mirror
 torch
for demonstration and comparison
 a variety of mirrors and reflective surfaces e.g. make
up/shaving mirror, wing mirror, spoons, shiny metal tray.
 some letters that will stand up.
 laser pointer (optional)
Health and Safety
The mirrors for the students should all be plastic. If students
are allowed to handle any glass mirrors for comparison then they
should take extra care. If using a laser pointer take care not to
shine it directly in anybody’s eyes.
Lesson Plan
Discuss reflections, where have they seen them. Are they always
a “true” image?
Show letters in a flat mirror to
emphasize that mirrors do not turn
things round only show exactly what
faces them.
Students can use the plane mirrors to investigate looking at
objects around the classroom. This can be to see how different
pictures, writing and objects appear when reflected and also to
see how the angle you hold the mirror at affects what you see.
Combining mirrors is also fun.
Allow students to investigate images in the flexible mirror. Have
they ever been in a hall of mirrors? How can the mirror change
their image?
Introduce the concave/convex mirrors.
Concave
Convex
Allow students to explore the images. Students can then use a
torch shining on the mirror to see how the light is affected.
Show the students the real mirrors. Wing mirrors are convex as
they allow the driver to see more of the road, however the image
is smaller. Shaving/make up mirrors are concave so that the
image in them is enlarged and more detail is shown.
As a final challenge you could ask the students to set up a mirror
maze. Can they get the torch light from the torch in one corner
of the table to a point specified by you? The path of the light
will show up better with a laser pointer so you could ‘test’ their
mazes.
Teacher notes
Light is reflected at the same angle that it is incident upon the
surface at. A curved surface acts as a little mirror at each point,
each little mirror is at a different angle.
To study reflection further, students should consider the path of
the ray and so discussion should focus on the light travelling from
a point to the mirror and then on to somewhere else. Light
travels in straight lines.
Although mirror images are often said to be laterally inverted
that isn’t strictly true. My right hand does not appear at the left
side of the image only as what would be the left hand for the
person in the image.
Combining mirrors in order to see round corners can be explained
by considering the path of the light ray. This is of course how a
periscope works and you will find a template with this pack if you
want to make one with your pupils.
Concave mirrors converge (bring together)
light. Close up to the mirror and the
image is virtual, magnified and right way
up. Further away and the image is real,
magnified and upside down. Even further
away and the image is real, smaller and
upside down. Real images can look like
they exist as a solid object, which is the
basis of some magic tricks.
Convex mirrors diverge (spread out) light.
No matter how close to the mirror you are
the image is always virtual, right way up
and smaller.
This information is well beyond primary school pupils but they
should be able to notice when the image is right way up/inverted
and when it is magnified/diminished. For more information for
teachers try this applet
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=48
The hall of mirrors combines mirrors
bent both inwards and outwards, both
vertically and horizontally in order to
distort the image. Pupils should be
able to see that bits that bend out
make the reflection smaller at that
point and bent in bits produce a larger
image. The expansion occurs either vertically or horizontally
depending on how the mirror is bent.
Further activities:
Make a periscope.
Play with words and images on a computer to see how stretching
bits in one dimension alters. This could also link with maths as
the area of a rectangle could be compared when it is stretched in
one dimension by a factor of 2,3 or 4 and then in 2 dimensions.
Reflection has a place in both poetry and art. A quick internet
search will reveal lots of examples.
Physical activity, mirror the movements of another person and
then alternatively copy them exactly.