Experiment 21-Geometric Optics

Part 1-Parallax (set up)

• Draw one line down the

middle of the long side

of the paper

• Draw a line

perpendicular to the

first line along the short

side of the paper

• Place the mirror along

the short line

• Place a pin anywhere

along the normal in

front of the mirror

Part 1-Parallax (perpendicular lines)

• Line up horizontal

line at bottom of

protractor with

already drawn line

• Perpendicular line

will be at 90o

Part 1-Parallax (method)

• Notice the reflection of

the first pin in the mirror.

THIS IS OBJECT 1

• Place a second pin on the

normal behind the mirror.

THIS IS OBJECT 2

• Look to the left (or right)

of the closer pin

• At first the reflection and

the second pin you placed

won’t line up

• Move object 2 so that it

lines up with object 1 (but

keep object 2 along the

normal)

Part 1-Parallax (method)

• Notice that the reflection

of the front pin (object 1) is

lined up with the back pin

(object 2)

• Good job

Part 2-Reflection (set up)

• Draw two

perpendicular lines

and place mirror

along the short line

(like part 1)

• Use the protractor

to draw a line

between 25o-35o

• Place two pins

along this line and

label them P1 and

P2

Part 2-Reflection (method)

• Move your head so that

the reflection of both pins

in the mirror align with

one another

Part 2-Reflection (method)

• Place down two pins so that they

line up with the reflections of P1

and P2

• Label these pins P3 and P4

• Draw a line connecting P3 and P4

Part 2-Reflection (method)

• Top down view of final result

Part 3-Refraction (set up)

• Place square plexiglass

in center of page

• Trace its outline

Part 3-Refraction (set up)

• Draw a normal line from the top

left corner of the outline (2 cm)

• Use the protractor to draw a line

between 25o-35o from the normal

(like in part 3)

• Place two pins along this line and

label them P1 and P2

Part 3-Refraction (method)

• Place the square lens on

top of its outline

• Look through the bottom

of the lens to find the

image of P1 and P2*

* You can place a blank sheet

of paper behind the lens to

make this easier for you

Part 3-Refraction (method)

• Move your head so

that the images of

the two pins line up

with one another

Part 3-Refraction (method)

• Place two pins down so

that they line up with the

images of P1 and P2

• Label these new pins P3

and P4

Part 4-Total Internal Reflection (set up)

• Place triangle plexiglass

lens on paper and trace its

outline

Part 4-Total Internal Reflection (set up)

• Draw a line perpendicular to

the left vertex of the long

side on the lens (like in part

4) 1 cm from the vertex

• Place two pins along this

line and label them P1 and

P2

Part 4-Total Internal Reflection (method)

• Look through the bottom of

the lens and line up the

images of P1 and P2 (like in

part 4)*

*You can place a blank sheet of

paper behind the lens to make

this easier for you

Part 4-Total Internal Reflection (method)

• Place down two pins so that

they align with the images of P1

and P2 (like part 4)

• Label these two pins P3 and P4

Part 4-Total Internal Reflection (method)

• Draw a line connecting P3 and

P4 with the base of the lens

outline

• Extend these lines through the

lens outline to the far side of

the triangle

• Draw a line across the triangle

connecting the extensions of

P1P2 and P3P4

• Top down view of the final

result