PHYS 1407 – Conceptual Physics II
Image Formation with Mirrors

 

Leader: _____________________________  Recorder: ___________________________

Skeptic: _____________________________ Encourager: _________________________

 

Materials

Concave Mirror

Convex Mirror

Plane Mirror

CD

 

Introduction

      When you look at yourself in a mirror you see what is called your image.  The image is formed by your eye as it processes the light reflected from the mirror.  The eye is integral to seeing images although we often refer to the images as being formed by the mirror.  Different shapes of mirrors can from different types of images.  In this activity we will explore some aspects of the images formed by mirrors.

 

Part 1 Image Formation with Plane Mirrors

Hold the plane mirror at arms length.

 

Q1)  Describe your image in terms of size and orientation.

 

 

Move the mirror closer to you.

 

Q2)  Does the image appear to change in anyway as you move the mirror closer.

 

 

Try the following.  Look at something in the distance and then rapidly shift your gaze to something nearby.

 

Q3)  When you shifted your gaze, was the nearby object already in focus or did your eyes have to adjust?

 

 

We can use this idea to determine if two things are at the same location.  Hold one index finger about a foot in front of your face.  Hold the other index finger at arms length in front of your face.  Shift your gaze back and forth between them.

 

Q4)  Are the fingers already in focus when you shift back and forth or do your eyes have to adjust?

 

Focus on the distant finger.

 

Q5)  Is the front finger still in clear focus?

 

 

Focus on the front finger.

 

Q6)  Is the distant finger still in clear focus?

 

 

Hold both fingers together at arms length.

 

Q7)  Are they both in clear focus?

 

 

Q8)  If both objects are the same distance then you focus on them simultaneously?

 

 

Q9)  If two objects are at different distances, can you focus on them simultaneously.

 

Hold the plane mirror at arms length again and view your image,

 

 

P10)  Where do you think the image is located?

 

 

Hold the CD by placing your small finger in the center hole so that your small finger and the shiny side of the CD face you.  Hold the CD at arms length.

 

Find your image in the CD.  Switch back and forth between your image and the your small finger in the center of the CD.

 

Q11)  Are they both in focus at the same time or do your eyes have to adjust?

 

 

Q12)  Is the image at the same location as your finger?

 

 

Q13)  Is it correct to say the image is “in the mirror”?

 

 

Hold you small finger about a foot in front of your face and then move it backwards.

 

Q14)  As you move the finger backwards, does the size it appears to you change?  If so, in what way?

 

 

 

Hold the CD at arms length with your small finger in the center as before.  Place the small finger of your other hand about halfway between you and  the CD so that you can see its image in the CD.

 

Q15)  Do the finger holding the CD and the image of your other finger appear to be the same size, or is one bigger than the other?  If one appears bigger, which one?

 

 

 

Q16)  If one appears bigger, then is it closer, the same distance, or further away than the other?

 

 

Q17)  Would you say that the image of your finger is located in front of the mirror, in the mirror, or behind the mirror?  Explain your answer based on your observations.

 

 

 

 

Part 2 – Image Formation with Curved Mirrors

Hold the large concave mirror at arms length and observe your image.

 

Q!8)  Describe your image in terms of size and orientation.

 

 

Move the mirror towards you while observing your image.

 

Q19)  Describe how the image changes as you bring the mirror towards you.

 

 

Q20)  Describe what happens to your image when the mirror is quite close to your face.

 

 

 

Hold the large convex mirror at arms length.

Q21)  Describe your image in terms of size and orientation.

 

Move the mirror towards you while observing your image.

 

Q21)  Describe how the image changes as you bring the mirror towards you.

 

 

 

Q22)  Describe the image in the convex mirror when it is quite close to your face.  How is this different than what you observed in the concave mirror?