Physics
Lab 3.6 Plane Mirror
Overview
In this laboratory we
study the nature of the virtual image formed by a plane
mirror.
We also study the multiple
images formed by two mirrors at an angle to each other.
Experiments
- Mirror image
- Angles of incidence
and reflection
- Multiple images
Experiment
1: Mirror Image
Equipment
- Plane mirror –
mounted vertically on a stand or block of wood.
- White paper.
- Object (Any
unsymmetrical object)
Procedure
- Mount the mirror
vertically on top of a piece of paper.
- Draw a line on the
paper to indicate the position of the reflecting
surface. (The mirror line)
- Place the object a
short distance in front of the mirror so that the
image of the object can be completely seen. Mark
the position of the object on the paper.
- Measure the distance
from the object to the mirror.
- Estimate the position
of the image behind the mirror. Mark the position
of the image on the paper.
- Measure the distance
between the image and the mirror.
- Draw a line from the
position of the object to the position of the
image.
Questions
- How does the distance
of the image behind the mirror compare with the
distance from the object to the mirror?
- What is the angle
between the line from the object to the image and
the mirror line?
- Does the image appear
to have a different size to the object?
- Is the image
vertically inverted?
- Is the image
laterally inverted?
Experiment
2: Angles of Incidence and Reflection
Equipment
- Plane mirror –
mounted vertically on a stand or block of wood.
- White paper.
- Light source –
narrow vertical beam
- Protractor
Procedure
- Place the mirror on
the paper and mark the mirror line.
- Shine a beam of light
at an angle to the mirror.
- Mark the incident ray
and reflected ray on the paper.
- Draw a line at right
angles (normal) to the mirror line at the point
where the incident ray and reflected ray coincide
with the mirror line. (The incident point)
- Measure the angle
between the incident ray and the normal. (Angle
of incidence)
- Measure the angle
between the reflected ray and the normal. (Angle
of reflection)
- Compare these two
angles.
- Move the mirror so
that it rotates by 10º around the incident point.
- Measure the angles of
incidence and reflection.
- Repeat the experiment
using various angles of incidence.
Questions
- If the mirror is
rotated by 10º around the incident point, by how
many degrees does the reflected ray change?
- Does moving the
mirror change the relationship between the angle
of incidence and the angle of reflection?
Experiment
3: Multiple Images
Equipment
- 2 plane mirrors
– mounted vertically with a common edge so
that the angle between the mirrors can change
- Small object
- Protractor
Procedure
- Measure the angle
between the two mirrors
- Place a small object
between the two mirrors
- Count the number of
images that can be see when looking at the
mirrors.
- Change the angle
between the mirrors and repeat the experiment
Question
- How does the angle
between the mirrors affect the number of images
that can be seen?
- How does a
kaleidoscope work?
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