Reflection and Refraction
Reflection and refraction are two commonly observed optical properties of light. Whenever light strikes the surface of some material at an angle, part of the wave is reflected, and part is transmitted (or absorbed). The reflection of light rays from a plane surface such as a glass plate or a plane mirror is described by the law of reflection:
Figure illustrating the law of reflection from a mirror with arrows representing light rays. Instead of measuring the angles of incident and reflected rays from the mirror that is the reflecting surface, it is customary to measure them from a line perpendicular to the plane of the reflecting surface. This imaginary line is called the normal. The incident ray, the normal, and the reflected ray all lie in the same plane. The incident ray and normal ray form an angle of incidence. The reflected ray and normal ray form an angle of reflection.
Law of reflection : θi = θr
The angle of incidence (θi) is equal to the angle of reflection (θr).
These angles are measured from a line perpendicular or normal to the reflecting surface.
Refraction: represents a change of direction that light undergoes when it enters a medium with a different index of refraction from the one through which it has been traveling — for example, when, after moving through air, it passes through water.
Figure illustrating refraction of a ray of light incident upon a body of water. The angle of incidence is larger than the angle of refraction by an amount that depends on the relative speeds of light in air and in water. The path of least time is shown by the dashed line, which clearly is not the path of the shortest distance.
Law of Refraction: n1 sin ๐1 = n2 sin ๐2
n1 = index of first material
๐1 = angle of incidence
n2 = index of second material
๐2 = angle of refraction
Procedure
The lab activity uses a simulation developed by the University of Colorado at Colorado Boulder.
Refraction and Reflection Click here
Choose “Intro”
A.
1. Select Material 1 [top Material] is Air
2. Index of Refraction is n1=1
3. Select Material 2 [Bottom Material] is Water
4. Click on Red button,
5. Use protractor and adjust the angel of incidence ๐1 = 300
6. Record in the table n2 and ๐r and ๐2
Material 1: Air
n1 = 1
๐1 = 300
๐1 = 300
Material 2: Water
n2 =
๐r =
๐2 =
Q1. What is the happening with the laser beam at the interface between air and water? Are both reflection and refraction laws verified?
B. Repeat steps 1 to 5 but adjust the mediums and angles to the values indicated in the table below.
Material 1: Air
n1 = 1
๐1 = 300
๐1 = 300
Material 2: Glass
n2 =
๐r =
๐2 =
Q2. What is the happening with the laser beam at the interface between air and glass? Are both reflection and refraction laws verified?
C. Repeat steps 1 to 5 but adjust the mediums and angles to the values indicated in the table below.
Material 1: Air
n1 = 1
๐1 = 300
๐1 = 300
Material 2: Air
n2 =
๐r =
๐2 =
Q3. What is the laser’s beam path?
D. With medium 1- water and medium 2-air slowly increase the incident angle between 300 and 600
Describe what is happening.
What is the name of this phenomenon?
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