Experiment 9: Concave and Convex Mirror

Purpose:
The purpose of this experiment is to study the properties of the concave and convex mirror. Students will examine the mirrors by placing the object in front of the mirrors in different distances and observing the images in the mirrors.
Procedure:
1. Obtain a convex mirror, concave mirror, object which is a marker, ruler.

2. Experiencing the convex mirror:

A.  Place the marker in front of the convex mirror and describe the image characteristics:

- The image appears smaller than the object.
-The image is upright.
-The image is located behind the mirror.
B.  When moving the object closer to the mirror, the image is getting bigger. Once the object is close the mirror, the image is as same size as the object.

C.  When moving the object further from the mirror, the image is getting smaller.
D. Measure the distances and the heights of the object and the image.

d₀ = 50±2 cm

h₀= 12±1 cm

h_i = 4±1cm

d_i/h_i = d₀/h₀  → d_i = d₀h_i/h₀ = 50*4/12 = 16.67 cm

E. Calculate the magnification:

m= h_i/h₀ = 4/12 = 0.333

F. Sketch the image using the light ray diagram.

Yes, our observations agreed with the light ray sketch.

3. Experiencing the concave mirror:

A. Place the object in front of the mirror and describe the image characteristics:

- The image appears larger than the object.

- The image is inverted.

- The image is located between the mirror and the object.

B. When moving the object closer to the mirror, the image is getting bigger. At one point, the image appears upward behind the mirror and is smaller than the object.Once the object is close to the image is as same size as the object.

C.When moving the object further from the mirror, the image is getting smaller.

D. Measure the distances and the heights of the object and the image.

d₀ = 1000±2 cm

h₀= 12±1 cm

h_i =16.5±1cm

d_i/h_i = d₀/h₀  → d_i = d₀h_i/h₀ =100*16.5/12 = 137.5 cm

E. Calculate the magnification:

m= h_i/h₀ = 16.5/12 = 1.375

F. Sketch the image using the light ray diagram.

No, our observations did not agree with the light ray sketch. The image which we observed is bigger than the object. The reason is that we might place the object a distance closer than radius of the mirror.

Summary:

For the convex mirror, we always get the image is virtual and upright, and smaller than the object. As moving closer the the mirror, the image is getting bigger.

For the concave mirror, we can have the image is virtual or real, upright or inverted depending on where we place the object.

Experiment 7: Introduction to Reflection and Refraction

Purpose:
The purpose of this experiment is to examine the reflection and refraction of the light. By using the light ray traveling through the semicircle plastic, students will collect data of the light's refraction. Once data are collected, the graph of the refraction's angles will be plotted. Using the the logger-pro program to get the trend line of the plot. The slope of the plot is the plastic's index of refraction.

Procedure:
1. Obtain a light box, semicircle plastic, a circular protractor and the Pasco optical kit.

2. Set the light ray traveling in the plastic that starts at the mid-point of the flat side of the semicircle.

3. Answer the questions in the lab manual before get started.
a. What is the angle of the incidence for the light ray at the flat surface? - answer is 0 degree
b. What is the angle of the refraction at the flat surface? - answer is 0 degree
c.What will happen to the light ray as it leaves the plastic piece at the curved edge and goes into air? - Answer is the light will go straight into air. Because the light ray is a straight light, it will be a straight light when it comes out.
d. will this experiment be a situation where light travels from a material of greater density to one of lower density or from lower density to higher density? - Answer is this experiment is a situation of the light travels from the lower density to higher density.

3.Now turn on the light and see if the predicted answers are correct. - yes, they are.

4. Collecting data, the angle of incident is Theta 1, and the angle of the refraction is Theta 2.

Trial	Theta 1	Theta 2	Sin (theta1)	sin (theta2)
1	0	0	0	0
2	5±0.5	2±0.5	0.087153179	0.03489847
3	10±0.5	7±0.5	0.173643108	0.12186577
4	15±0.5	11.5±0.5	0.258811587	0.19936213
5	20±0.5	15±0.5	0.342010469	0.25881159
6	25±0.5	18±0.5	0.422606599	0.30900818
7	30±0.5	21±0.5	0.499986627	0.35835786
8	40±0.5	26±0.5	0.642771837	0.43835912
9	50±0.5	31±0.5	0.766027899	0.5150244
10	60±0.5	36±0.5	0.866009961	0.58777026
11	70±0.5	41±0.5	0.939680297	0.6560431

5. Plot the graph of Theta 1 and Theta 2.

The equation which we think would fit the curve is quadratic equation.

6. Plot the graph of Sin(theta1) vs. Sin(theta2).

The slope of this graph is 1.45. The slope represents the ratio of the index refraction of the plastic and the air.
The straight light equation: y = 1.453x - 0.005683.
Slope is equal to sin(theta2) / sin(theta1) = 1.453

7. Set up the new arrangement of the equipment.

8. Answer the questions in the lab manual.
a. What will happen to the light ray when it first curved surface of the semicircle pirsm when it is in the position shown? - answer is the light ray goes through the plastic as a straight light.
b. The reason is the angle of incident is zero, so the angle of refraction is also zero.
c. The light ray will come out the flat surface and make the refraction when it goes into air.
d. The experiment will be a situation where the light travels from the higher density to lower density.
9. Rotate the protractor and prism, start collecting data.

Trial	Theta 1	Theta 2	Sin (Theta1)	Sin (Theta2)
1	0	0	0	0
2	5±0.5	4±0.5	0.08715318	0.06975442
3	10±0.5	12.5±0.5	0.17364311	0.216433332
4	15±0.5	20±0.5	0.25881159	0.342010469
5	20±0.5	27±0.5	0.34201047	0.453978116
6	25±0.5	39±0.5	0.4226066	0.62930479
7	30±0.5	52±0.5	0.49998663	0.787994274
8	40±0.5	84±0.5	0.64277184	0.994517375
9	42±0.5	90	0.7660279	0.999999999
10	60±0.5	90	0.86600996	0.999999999
11	70±0.5	90	0.9396803	0.999999999

 
10. We were no able to complete 10 trials because the refraction disappears (at 90 degree) when the incident ray is at 42 degree.

 
11. Plot the graph sin(theta1) vs. sin(theta2).

 The slope represents the ratio of the plastic's index infraction and air's index infraction.

The equation of the straight line is y = 0.5823x + 0.0548.
This is not the same equation on the earlier experiment.

 Summary:
According to the purpose of this experiment, we are going to study the reflection and refraction of the light ray through different density. As the results, the light ray is changing angle differently when it goes through different density. It means that the angle of the refraction depends on the index refraction. The ratio between Sin angle of the incident and sin angle of the refraction is inversely proportional to the ratio between index refraction of two materials.