PASCO WA-9899 Ripple Tank System - Manual (Page 25)

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M o d e l N o . W A - 9 8 9 9 E x p e r i m e n t 5 : I m a g e F o r m e d b y a P l a n e M i r r o r
25
Experiment 5: Image Formed by a Plane
Mirror
Purpose
The purpose of this activity is to show how the position of the image formed by a
plane mirror relates to the position of the object.
Theory
When wave fronts reflect from a plane mirror’s surface, the angle of inci-
dence of the ray equals the angle of reflection of the ray. The image formed
by a plane mirror appears to be a certain distance behind the mirror. This dis-
tance is called the ‘image distance’. The distance of the object in front of the
mirror is called the ‘object distance’. The relationship of the angles of inci-
dent rays and reflected rays can be used to find the relationship of the ‘image
distance’ to the object distance. See Figure 5.1.
Setup
1. Mount the light source onto its rod at the back edge of the ripple tank.
2. Pour a small amount of water into the tank and adjust the feet on the legs
of the tank to level the tank.
3. Place the long straight barrier in the middle of the tank and add about 800 mL of
water to the tank (or enough water so that the water level is about halfway up the
long straight barrier.)
4. Use a rod and base to support the ripple generator and position the generator over
the midpoint of one side of the ripple tank. Adjust the generator so that one ripple
arm is in line with the center of the tank.
5. Plug the light source into the ripple generator and connect the ripple generator to
its power adapter.
6. Connect a single standard dipper to one of the ripple arms. Adjust the ripple gen-
erator until the bottom of the standard dipper is barely in contact with the surface
of the water.
7. Place a sheet of paper directly under the ripple tank so you will be able to sketch
the images of the waves that are projected onto the sheet by the light source.
Equipment from Ripple Tank System
Ripple Tank Ripple Generator and Light Source
Long Barrier Standard Dipper
Ruler
Other Equipment and Materials
Large Rod Stand (ME-8735) Paper (about 40 cm by 40 cm)
90-cm Rod (ME-8738)
mirror
object image
Figure 5.1: Plane Mirror
reflected rays
incident rays