Refraction

Type of Project: Experiment based, practical interaction, Question and answer

Grade: 8th

1. Summary:

After the interactive session with two science teachers in presence of HM & Computer teacher (facilitator). Coordinator initiated the interactive mode of this topic by teachers & students to understand the concept of refraction (Bending of light).

2. Time required: 1 class for their curriculum to cover up & another 1 class for the demonstration & interactive Q & Ans session which accounts for about 1 ½ hours at a stretch.

3. Materials required

· A glass tumbler

· A pencil/pen

· Water

· Tray

· Prism

· Chart Paper

· A Sharpened Pencil

4. Process Documentation

A) Discussion with concerned teachers about Refraction

After the discussion with science teachers & facilitator, the science teacher() has taken a glass tumbler & put water inside it. Then a pencil/pen is inserted into the glass tumbler & shown to the students & introduced the word refraction, bending nature , medium of light, incident light, normal, refracted ray, Snell’s law, angles of refraction etc. which usually denotes the basic of bending nature of light.

The following concept were discussed


BACKGROUND INFORMATION AND QUESTIONS

1. How light moves in vacuum or in our atmosphere ?

Ans:

2. What is meant by refraction of light ?

Ans:

3. Is refraction of light different from reflection or not ?

Ans:

4. What is the role of different media in refraction of light ?

Ans:

5. Give some common examples of refraction of light ?

Ans:

B)

Experiment procedures (i)

1. The experiment was carried out in a tray which contains tumbler with water

2. Then a pencil/pen is inserted into water.

3. The oblique view of the pen/pencil from the top showed the pencil/pen to be a bent material.

Experiment procedures (ii)

This experiment of Rainbow was carried out by their teacher & then some students along with me also experienced

1. Little volume of water is taken in jaw & then forcefully sprayed back to the side of sun into the atmosphere which creates a deep layer of fog like atmosphere in which when sunlight passes through makes an artificial rainbow which was then understood by their teacher.

2. The phenomenon of rainbow is made when light bends while moving from lighter medium of normal air to the denser part of air which contains the artificial fog created by us (teacher) which depicts the spectrum of solar white light.

3. Spectrum of white light was easily understood when the teacher had shown prism to the solar light (this spectrum was carried out after this experiment)


Laws of Refraction

1st law: Incident ray, the normal drawn on the surface of refraction & refracted ray lie in one plane.

2nd law : For two definite medium & for one light range the sine of angle of incidence & sine of angle of refraction is a constant.

Sin i/sin r = m

(In a right angled triangle for any acute angle, the ratio of perpendicular & hypotenuse is known to be sine of that angle.)

5. Exploring Facts

Refraction and Sight

We are able to see because light from an object can travel to our eyes. Every object that can be seen is seen only because light from that object travels to our eyes. As you look at students in class, you are able to see students because they are illuminated with light and that light reflects off of them and travels to your eye. In the process of viewing any student, you are directing your sight along a line in the direction of that student. If you wish to view the top of student's head, then you direct your sight along a line towards the top of her/his head. If you wish to view student's feet, then you direct your sight along a line towards student’s feet. And if you wish to view the image of student in a mirror, then you must direct your sight along a line towards the location of student's image. This directing of our sight in a specific direction is sometimes referred to as the line of sight.

As light travels through a given medium, it travels in a straight line. However, when light passes from one medium into a second medium, the light path bends. Refraction takes place. The refraction occurs only at the boundary. Once the light has crossed the boundary between the two media, it continues to travel in a straight line. Only now, the direction of that line is different than it was in the former medium. If when sighting at an object, light from that object changes media on the way to your eye, a visual distortion is likely to occur.

The diagram at the below shows a view of the light path from the submerged portion of the pencil to each of your two eyes. Only the left and right extremities (edges) of the pencil are considered. The black lines depict the path of light to your right eye and the red lines depict the path of light to your left eye. Observe that the light path has bent at the boundary. Dashed lines represent the extensions of the lines of sight backwards into the water. Observe that these extension lines intersect at a given point; the point represents the image of the left and the right edge of the pencil. Finally, observe that the image of the pencil is wider than the actual pencil.


6. Figures

Figures (Refractive index)

7. Project Learning Outcome

1. Direct learning: Light movement

2. Concept Learning: Bending nature of light, Illusion caused by light rays, Laws of refraction

3. Incidental learning: Reflection of light, formation of image & rainbow, MS paint, Ms Word

8. Reference:

Marching Soldiers analogy which will be done in our next activity.