Refraction Exploration

Purpose:

The purpose of this activity is to explore the behavior of a ray of light at the boundary between
two materials. Variables that would affect the behavior of light will be investigated.

Background:

This activity centers on the behavior of light when it reaches the boundary or interface that
separates two materials. To begin, look up, read about, and define the following terms. (You
could consider using the Search bar on The Physics Classroom.)

o Reflection: The simple phenomenon of light bouncing back after striking an object.
o Refraction: The bending of a light wave's path as it passes across the boundary.
Separating two media caused by the change in speed experienced by a wave when it
changes medium.
o Transmission: The movement of electromagnetic waves (whether visible light, radio
waves, ultraviolet light, etc.) through a material.
o Angle of Incidence: The angle between the normal and the ray of light.
o Angle of Refraction: The angle formed by the refracted ray with respect to the normal
line.
o Index of Refraction: Values indicating the relative speed of a light wave in a specific
medium.

Navigate to the Refraction Interactive in the Physics Interactives section of The Physics
Classroom's website. Explore the environment - move the laser, fire the laser, manipulate the
protractor to measure angles, change the top and bottom substance and observe all results.
Once you're familiar with the environment, begin exploring the questions listed in the next
section. Your teacher will tell you how many questions and/or which questions to explore.

As you tackle a question, think about what variables you will change variables and what
variables you will keep constant; and think about what observations and/or measurements you
must make in order to answer the question. Record your findings and then answer the question
using a claim-evidence-reasoning format. The claim is the answer to the question; the evidence
is a reference to collected data that have been recorded; and the reasoning is a clear and
logical discussion of how the evidence supports the claim that you are making.

Your teacher will give you instructions as to how and where you will record the data and
conclusions for each question that you are assigned.
Questions:

1. Are there conditions under which the incident light ray undergoes reflection but not
transmission at the boundary? If so, then what are those conditions?
Yes, when the top substance is denser than the bottom substance, the incident light ray
undergoes reflection but not transmission at the boundary. Such as when the top substance
are oil, diamond, unknown #1, unknown #2, and randomize, and the bottom substance are
vacuum, water, and air. When these substances partnered up, there won’t be any
transmission, only reflection.

2. Are there conditions under which the incident light ray undergoes transmission
across the boundary without actually bending (or refracting)? If so, then what are
those conditions?
Yes, when the top and bottom substance are the same. For example, air to air, water to
water, vacuum to vacuum, diamond to diamond, and so on.

3. The amount of light that undergoes reflection or transmission is demonstrated by

4. What affect does an increase in the angle of incidence have upon the angle of
reflection?
As the angle of incidence increases, the angle of reflection also increases. It is because
of the law reflection states that when the light rays strike a smooth surface, the angle of
reflection is equals the angle of incidence.

5. What affect does an increase in the angle of incidence have upon the angle of
refraction?
As the angle of incidence increases, the angle of refraction decreases; such as any
angle of incidence greater than 48.6 degrees would not result in refraction.

6. Under what conditions are the angles of incidence greater than the angles of
refraction?
If a light ray crosses a boundary from a slow-moving material to a faster-moving material,
like water into air, the light ray will bend away from the normal line. And the angle of
refraction would be greater than the angle of incidence when the light waves would refract
away from the normal line.

7. Every substance has its own unique index of refraction (n). For light passing from air
to another material, what affect does increasing the angle of incidence have upon the
angle of refraction?
As the angle of incidence increases, less refraction and more reflection are observed.
Because the brightness of the refracted ray decreases as the angle of incidence increases;
 while the brightness of the reflected ray increases, since the angles of reflection and
incidence are the same.

8. Under what conditions is the angle of incidence greater than the angle of refraction?
And under what conditions is the angle of incidence less than the angle of refraction?
The only way for the angle of refraction to be greater than the angle of incidence is for
light to bend away from the normal. It is due to light that only bends away from the normal
when passing from a denser medium to a less dense medium.

9. How does the index of refraction of Unknown #1 compare to the index of refraction of
oil?
Based on the simulation, the index of refraction of Unknown #1 is greater than the index
of refraction of oil, because the angle of fraction of Unknown #1 is less than the angle of
refraction of oil. The index of refraction is higher in denser substances that bend and change
direction as it enter the substance.

10. How does the index of refraction of Unknown #2 compare to the index of refraction of
oil?
The situation as just like in number 9. The index of refraction Unknown #2 is greater than
the index of refraction of oil, since the angle of fraction of Unknown #2 is less than the angle
of refraction of oil; which means that the Unknown #2 is also denser than oil.

11. Now think of your own testable question. Use the simulation to answer the question.
Which has the greater index of refraction: Diamond or Unknown #1?
Using the simulation, diamond has the greater index of fraction than the Unknown #1,
indicating that it is denser and light travels more slowly.