Question

Reflection and Refraction of Light

In this activity, the properties of reflection and refraction of light will be explored. The simulation shows the light rays as they are incident on a medium interface (incident ray), the reflected from the medium interface (reflected ray), and refracted into the second medium after crossing the interface (refracted ray). Additionally the angles made by each of these rays with respect to the normal (vertical black perpendicular to the interface) are displayed as wedges in different colors: angle of incidence (black), angle of reflection (blue), and angle of refraction (red). The numerical values for each are shown in the section to the right. The angle of reflection and the angle of refraction are determined by the angle of incidence and the index of refraction of the mediums used. The applet begins with air as the medium where the light ray starts and then the ray is incident on the second medium, water.

Instructions:

Go to http://www.walter-fendt.de/ph14e/refraction.htm

Use the applet to complete the tables below and assist in answering the following questions.

Case 1: Air-Water. Keep the configuration of the applet the same as when it opened. Fill in the table below.

Air →Water	Index of Refraction (Air)	1.0003
	Index of Refraction (Water)	1.33
Angle of Incidence (degrees)	Angle of Reflection (degrees)	Angle of Refraction (degrees)
10
30
45
60
80

                                 

1. The following three questions pertain to Case 1. Compare the angle of refraction to the angle of reflection for the set of incident angles used in the table.

2. State the direction in which the refracted ray bends (toward the normal or away from the normal). You can determine this from the diagram or from the comparison of refracted angle to reflected angle.

3. Is there a critical angle (resulting in total internal reflection) in this situation? Why or why not? If there is, what is its value?

Case 2: Water-Air. Change the top medium to water and the bottom medium to air. Fill in the table below.

Water →Air	Index of Refraction (Water)	1.33
	Index of Refraction (Air)	1.0003
Angle of Incidence (degrees)	Angle of Reflection (degrees)	Angle of Refraction (degrees)
10
30
45
60
80

4. The following three questions pertain to Case 2. Compare the angle of refraction to the angle of reflection for the set of incident angles used in the table.

5. State the direction in which the refracted ray bends (toward the normal or away from the normal). You can determine this from the diagram or from the comparison of refracted angle to reflected angle.

6. Is there a critical angle (resulting in total internal reflection) in this situation? Why or why not? If there is, what is its value?

Case 3: Diamond-Air. Change the top medium to diamond and keep the bottom medium as air. Fill in the table below.

Diamond →Air	Index of Refraction (Diamond)	2.42
	Index of Refraction (Air)	1.0003
Angle of Incidence (degrees)	Angle of Reflection (degrees)	Angle of Refraction (degrees)
10
30
45
60
80

7. The following three questions pertain to Case 3. Compare the angle of refraction to the angle of reflection for the set of incident angles used in the table.

8. State the direction in which the refracted ray bends (toward the normal or away from the normal). You can determine this from the diagram or from the comparison of refracted angle to reflected angle.

9. Is there a critical angle (resulting in total internal reflection) in this situation? Why or why not? If there is, what is its value?

Answer 1

Case 1

Air -> Water	Index of Refraction (Air)	1.0003
	Index of Refraction (Water)	1.33
Angle of Incidence (degrees)	Angle of Reflection (degrees)	Angle of Refraction (degrees)
10	10	7.5
30	30	22.1
45	45	32.1
60	60	40.6
80	80	47.8

1)

Angle of refraction is always less than angle of incedence in this case wheras angle of incidence and angle of reflection are always the same, Hence angle of refraction is always less than angle of reflection for the case of air to water.

2)

In this case refracted ray always bends towards the normal as can be observed from the values of angle of refraction given in the table.

3)

There is no critical angle or total internal reflection in this case because the light ray is travelling from an optically rarer medium to an optically denser medium.

Case 2

Water -> Air	Index of Refraction (Water)	1.33
	Index of Refraction (Air)	1.0003
Angle of Incidense (degrees)	Angle of Reflection (degrees)	Angle of Refraction (degrees)
10	10	13.3
30	30	41.7
45	45	70.1
60	60	-
80	80	-

4)

In this case for the first three values angle of refraction is greater than angle of reflection but for the last two values refraction does not occur (total internal reflection)

5)

In this case the refracted ray bends away from the normal as can be observed from the values in the table.

6)

There is a critical angle (resulting in total internal reflection) in this situation because the light ray is travelling from optically denser medium to optically rarer medium. The critical angle is 48.8⁰.

Case 3

Diamond -> Air	Index of Refraction (Diamond)	2.42
	Index of Refraction (Air)	1.0003
Angle of Incidence (degrees)	Angle of Reflection (degrees)	Angle of Refraction (degrees)
10	10	24.8
30	30	-
45	45	-
60	60	-
80	80	-

7)

In this case angle of refraction is greater than angle of reflection for first value of angle of incedence. For all other values of angle of incedence refraction does not occur (total internal reflection).

8)

In this case refracted ray bends away from normal as can be observed from the values noted in the table.

9)

There is a critical angle (resulting in total internal reflection) in this situation because the light ray is travelling from optically denser medium to optically rarer medium. The critical angle is 24.4⁰.