Mr. Kovall's Neighborhood

Return to Honors Physics Home Page (Revised 4-12-06)

Refraction of Light Through Geometric Figures

Purpose:

Materials:

Procedure: (None required for this lab)

Diagrams:  (triangle and rectangle-triangle combo)

EACH student must construct his/her own set of completed ray diagrams, including all required math solutions. Each student is being graded individually on the quality of his/her own lab diagrams and associated math solutions, so identify your personal work by writing your name on those pages. 

Each student's triangle diagram must display each of the following labels by writing the terms or phrases on the sheet.  For instance, you must identify the incident ray striking the triangle's surface by writing the words incident ray near the actual ray; the phrase ray bends toward normal must be written near the appropriate ray, with a light arrow pointing to that ray.

    (A) "incident ray" + arrow

    (B) "refracted ray" + arrow

    (C) "angle I", "angle R", "angle I'", angle R'" (use the angle symbol for "angle")

          (place actual measured values on same page as the diagram)

    (D) "air", "glass", "plastic".

    (E) "medium of lesser refractive index", "medium of greater refractive index"

    (F) "ray bends toward normal", "ray bends away from normal"

    (G) "reflected ray from internal reflection", "angle r" (angle of reflection)

You must submit the ORIGINAL DIAGRAMS, not a traced copy.  Your diagrams must also have perfectly formed normal lines, arcs depicting relevant angles between normal and ray, clearly drawn straight line rays, arrows, etc.

Sample Calculations: (seven solutions as demonstrated in class) ( R = rectangle, T = triangle, A = air)

n_R,A

n_A,R  and  (1/n_A,R = n_R,A)

n_T,A

n_T,R = n_T/n_R  and  n_T,R = sin I_R/sinR_T

    Ø_C

Conclusion:

    (A) Define refraction

    (B)  State the three laws governing refracted rays, relative to the geometric figures.

    (C)  Using the rectangle, state the relationship between the angles in the following pairs.  Explain the

meaning of each relationship, and provide actual angle data values:    angle I  vs. angle R;  angle I' vs.

angle R';  angle I vs. angle R';  angle R vs. angle I'.

    (D) State Snell's law. Explain its specific use in this lab.

    (E) Compare "n_R,A"  and "n_T,A. Explain differences (but NOT in terms of density) and provide actual values.

    (F) Compare "n_R,A" and "n_A,R" for the rectangle.  Explain how and why they are related.  Provide actual

values.

    (G) Explain the meaning of  "n_T,R". Compare values determined by two methods for the index of refraction

of the triangle relative to glass.  Provide actual values.

    (H) Compare the two angles (∟I’ and ∟r) associated with internal reflection in the triangle.

State actual values.

    (I) Do the calculated densities of the rectangle and triangle follow the indices of refraction for the two

geometric figures?  Provide a possible reason.

    (J) Compare the calculated critical angle with the measured angle of internal reflection.  What is the

significance of the difference between these values?

    (K) compare the exit refraction of the ray through the rectangle alone to that of the rectangle when the

triangle is placed against it. Explain, using actual data values.

Practice problems:  Complete short answer problem requiring you to diagram the path a ray of light would take when moving from air into a bubble of water and from water to a bubble of air.  Show an accurately drawn set of tangent and normal lines, with refracted rays moving through and from the bubbles.  You do not have to measure the angles, or determine an index of refraction.

You may also be required to complete two other short answer problems, including complete diagrams.  The teacher will clarify.

Three Sources of Potential Laboratory Error: 

        (state each mechanical source of error + affected variable(s) + specific data values)