Name:
Partners:
Refraction of Light and the Index of Refraction
Description of the Lab Activity
Purpose: To determine the behaviour of light when it passes from one medium to another.
Materials and Equipment (per group of 3 students):
-
1 transparent semicircular prism
1 light box with single slit or laser pointer
1 clear ruler and protractor
Sharp pencil and sharp coloured pencils
Observation Templates 1 and 2 (included with this lab document)
Procedure:
Part 1: Light Entering Prism From Air
1. Place the semicircular prism on Observation Template 1 in the outline as indicated.
2. Direct a ray of light toward the prism along each of the six rays on the drawing, starting with the ray along the
normal line. Draw the refracted ray that results from each of the incident rays.
3. M Measure the angles of incidence and refraction, from the normal line, and complete Table 1 below.
Part 2: Light Emerging From Prism Back Into Air
1. Place the semicircular prism on Observation Template 2 in the outline as indicated.
2. Direct a ray of light toward the prism along each of the six rays on the drawing, starting with the ray along the
normal line. Draw the refracted ray that results from each of the incident rays.
3. Measure the angles of incidence and refraction, from the normal line, and complete Table 2 below.
Data and Observations:
Table 1: Light Entering Prism From Air (cont’d on next page*)
Ray
1
2
3
4
Angle of
incidence (𝜃! )
Angle of
refraction (𝜃" )
𝑠𝑖𝑛𝜃!
𝑠𝑖𝑛𝜃"
𝑠𝑖𝑛𝜃!
𝑠𝑖𝑛𝜃"
5
6
*N.B. It is very bad practice to split a data table across two pages. Do as Mr. Gordon says, not as he does. 😊
Table 2: Light Emerging From Prism Back Into Air
Ray
Angle of
incidence (𝜃! )
Angle of
refraction (𝜃" )
1
2
3
4
5
6
Notes, Extra Observations, or Calculations
𝑠𝑖𝑛𝜃!
𝑠𝑖𝑛𝜃"
𝑠𝑖𝑛𝜃!
𝑠𝑖𝑛𝜃"
Analysis Questions
1. In both cases, what happened to the ray of light which traveled incident along the normal line (i.e. 𝜃! = 0°)?
2. What do you notice about the values of
"#$%!
3. What do you notice about the values of
"#$%!
"#$%"
"#$%"
in Part 1?
in Part 2?
"#$%
4. Is there any special relationship between "#$%! from Parts 1 and 2? Think carefully about the subscripts, and
"
the medium for which the ray was incident and in which it was refracted for Parts 1 and 2.
5. Table 3 below lists the indices of refraction for four common transparent media used to make prisms. Which
is the most likely material of the prism you used in this lab?
Table 3: Indices of Refraction for Solid Transparent Media
Medium
Acrylic
Crown Glass
Index of Refraction
1.47
1.54
Medium
Polystyrene
Flint Glass
Index of Refraction
1.61
1.68
Observation Template 1
Part 1: Light Passing from Air into the Prism
(1) Place the prism inside the
semicircle that best
corresponds to its size, with
the flat sides aligned.
(2) Direct the light toward
the flat surface of the prism
from the air.
(3) Mark the points where the
light leaves the prism, then remove
the prism to draw and label the
refracted rays. Measure and record
the angles incidence and of
refraction.
Observation Template 2
Part 2: Light Passing from the Prism into Air
(1) Place the prism inside the
semicircle that best
corresponds to its size, with
the flat sides aligned.
(2) Direct the light toward the
center of the flat surface of
the prism, through the curved
surface.
(3) Mark the points where the
light leaves the prism, then remove
the prism to draw and label the
refracted rays. Measure and record
the angles of incidence and of
refraction.