Periscopes

Periscopes

Pencil and paperOnline interactive
Overview
Using this Resource
Connecting to the Curriculum
Marking Student Responses
Working with Students
Further Resources
This task is about how light works through a periscope.
friends looking through a periscope
Draw a labelled diagram in the box below to show how the boy is able to see over the heads of the crowd using this box with mirrors. Your drawing will need to show:

  • the mirrors, (and angle they should be at),
  • the path the light takes, and
  • the direction of the light rays.

Question Change answer

Your drawing should show: the mirrors, (and angle they should be at), the path the light takes, and the direction of the light rays.
Task administration: 
This task can be completed with pencil and paper or by drawing online.
Level:
5
Curriculum info: 
Science, Knowledge, Physical World
Keywords: 
using physics, light, reflection, mirrors
Description of task: 
Task: draw a diagram showing how a periscope works. Assessment focus: reflected light.
Curriculum Links: 
Science capabilities
The capabilities focus is brought about by the conversations you have and the questions you ask.
 
Capability: Interpret representations
This resource provides opportunities to discuss converting text to light diagrams.
Science capabilities: 
Interpret representations
Answers/responses: 
 

Y10 (11/2003)
  • Mirrors positioned and angled as in diagram.
  • The path of light shown bouncing off both mirrors and travelling in a straight line; and
  • The correct light direction (heading in toward the eye).

          

NOTE: Accept any angle that actually works for the mirrors.
 
moderate
moderate
difficult

 

Diagnostic and formative information: 

Students' drawings showed many variations that revealed misconceptions that have been widely reported in science education research. Most students did appear to know that light travels in straight lines.

Many of the students placed arrows to show light travelling from the eye to the scene being viewed. The LISP project research showed that this is a very common misconception and is associated with an emphasis on the active nature of seeing . This could be challenged by comparing the visible features of eyes with the visible features of light sources.

The top two images below show how the incorrect positioning of mirrors created problems for some students. Either they did not know the laws for the path taken by reflected light, or the device they constructed led them to disregard these. (With the mirror flat to the sides of the tube, it is impossible to make the device 'work' without ignoring simple laws for the angles of incidence and reflection.) It is not possible from this evidence to say which explanation for the error is correct but this could be revealed in a quick conversation with the student.

The bottom image shows how even something as seemingly simple as the naming of angles can trip students up. It could be worth exploring the whole diagram as a series of symbolically connected parts, each of which has to be accurate to make the whole 'work' as intended.

  

Research
Osborne, R., & Freyberg, P. (1985). Learning in Science: The implications of children's science. Auckland: Heinemann. 

Research
Osborne, R., & Freyberg, P. (1985). Learning in Science: The implications of children's science. Auckland: Heinemann. 
 
Other ARB resources about reflection: