Reflecting Light Off a Plane Mirror
In this lab you will be investigating how light reflects off a plane (flat) mirror.
normal
Hypothesis: Predict what the relationship between the angle of incidence
and reflection will be.
Procedure: Trace the path of light as it reflects off a plane mirror
1. On the sheet of paper make a straight line in the middle where you will place the mirror (refer
to it as AB).
2. Make a mark on the AB line somewhere near the middle of the mirror (this is the point of
incidence).
3. Place the mirror so that the reflecting surface is on the line.
4. Aim the ray box so that the light hits the point of incidence and is reflected back along the same
line. Draw three small dots along this ray. Take the light away and connect the dots, with a ruler.
What does this line represent? (hint- look at diagram). Label it on your sheet.
5. Move the ray box and aim a ray at the point of incidence. Start with a large angle. Make small
dots along the incident ray and the reflected ray. Remove the mirror and connect the dots. Keep
moving the ray box to create different angles and draw the resulting incident and reflected rays.
Be sure to use different colors or numbers so you can see which incident and reflected rays go
together.
6. Use a protractor to measure the angle of incidence and the angle of reflection in your diagram.
Is there a pattern or similarities between the two angles? Fill in the following chart:
Colour or number of ray
Incident Angle
Reflected angle
Analysis;
1. Was your hypothesis correct?
2. Scientists use two laws to describe how light reflects from a plane mirror. The first law of
reflection from a plane mirror. The law of reflection compares the angle of reflection for light
rays hitting a mirror. What do you think the law of reflection says?
Viewing Images in a Plane Mirror
What are the characteristics of an image seen in a plane mirror?
Procedure:
1. Look into a large plane mirror:
a. What is the size (same, bigger, smaller) of the image compared to the object (you)?
b. What is the attitude (upright or upside down) of your image?
2. Place a piece of paper on the cardboard and draw a straight line a little longer than the mirrorlabel this line mirror.
a. Place the reflecting surface along this line
b. Draw an arrow 2- 3 cm long in front of the mirror. Label this ‘object’. Stick a pin in each
end of the arrow.
3. Move a pencil around behind the mirror until it is exactly where the image appears to be. Check
by looking at the image from several viewpoints.
a. When you are sure of the location make a mark on the paper. Do the same thing for the
second pin at the other end of the arrow.
4. Draw a dotted line connecting your two new marks and label it image.
5. Is the image real or virtual? (put a piece of paper where the image should be, if the image is
projected on the paper it will be real, if not it is virtual.
6. Remove the pins and measure the distance from the object to the mirror (this is the object
distance).
7. Measure the distance from the image to the mirror (this is the image distance). This will tell you
where the image is located in reference to the object.
Analysis:
1. What are the four characteristics of the image in your investigation? The four characteristics
are: attitude (1), size (1), location (7) and type (5).
2. How does the image location compare to the object location?
3. In some public areas one mirror is placed at an angle to allow people in wheelchairs to see
themselves. Draw a diagram to show how this would work.
4. What problems occur when printing or writing in a mirror? What could be done to make this
easier (hint think about how the word ambulance is written on the front of it).