LAB 5 Reflection and Refraction

Purpose

In this lab we are going to investigate the law of reflection

In addition, we are going to verify Snell's law

Discussion

Light can either reflect or refract when it is incident to a surface. The law of reflection is a simple equation that is used in many applications. It is expressed by the following

Equation 1: = (Law of reflection)

Where is the angle of incident and is the angle of reflection. If light is reflected, we use Snell's law to determine is path after its contact with a given surface (see figure 1). Snell's law is given by

Equation 2: sin = sin (Law of refraction),

Where is the incident index of refraction and is the refracted index of refraction. The index of refraction is an important concept, that is used in industry as is defined as the following,

= ,

Where c is the speed of light in a vacuum/air and its value is 3.0108 and v is the speed of light in the given material. For example the index of refraction is one for air.

Equation 4: % = 100%

Lab Report Components

o Practice Questions

o Data table

o Percent Error and calculations

o Statement on the accuracy of the experiment

o Concluding questions

Apparatus

Computer

Internet

Practice Questions

1. If water has an index of refraction of 1.33, what is the speed of light in water.

2. What is an industrial application of the index of refraction?

3. If light is moving through air and is incident on a surface of water at 15 degrees, what is the refracted angle?

Procedure

In your lab book you may share computer produced tables and graphs; all other work needs to be your own and original.

A. Angle of reflection

1. Open the following link to access the simulation. https://phet.colorado.edu/sims/html/bending-light/latest/bending-light_en.html

2. Select the More tools tab.

3. Place the protractor so that it is centered.

4. Make a table with 5 rows, one column will be titled incident angle, one column will be titled reflected angle and the last column will be titled percent difference.

5. Try five different incident angles and record the measured reflected angles.

6. Calculate the percent difference (they should be very close; measurements should be very accurate).

7. Record all data in the table and show a sample calculation.

B. Angle of refraction

1. Set the index of refraction for the top surface to 1.00.

2. Set the index of refraction for the bottom surface to 1.33 (water).

3. Make a table with the following columns: incident angle, experimental refracted angle measured, refracted angle theory and percent difference. This table should have five rows.

4. Record the experimental refracted angle for incident angles of 100 , 200 , 300 , 400 and 500 .

5. Using Snell's law calculate the theoretical refracted angle for each trial.

6. Determine the percent error.

7. Record all data in the table and show a sample calculation.

C. The speed of light in a material

1. Set the angle to 300 , this will be the same angle for all trials in this section.

2. Switch the bottom material to Mystery A

3. Make a table that has columns titled; measured refracted angle and refracted index of refraction. This table has two rows.

4. Solve equation 2 for .

5. Repeat step C4 for Mystery B.

6. Record all data in the table and show a sample calculation.

7. Search and find what material has a similar index of refraction for both A and B? (this may have many answers, since many materials have similar index of refractions just choose one answer for each, hint one possible material is very valuable and one possible value.

Conclusion

1. Were equations 1 and 2 verified in this experiment? Why?

2. What sources of error would occur in this experiment if it were not virtual?