INTRODUCTION
This article explains the concept of Rectilinear Propagation of Light and its application in real life. This is a literature review for this study and it is the continuation of Chapter One.
The chapter involves the views and opinions of authors and the order work piece which are in relation with the topic understudy. The review will be done under these themes;
1. Meaning of rectilinear propagation of light
2. Teaching techniques
3. Application of rectilinear propagation of light
4. Steps in rectilinear propagation of light
MEANING OF SCIENCE
Science is the intellectual and practical activity encompassing the systematic study of the structure on the behavior of the physical and the natural world through observation and experimentation, (oxford dictionary, 2003).
According to wester’s new collegiate dictionary (2000), science is the knowledge attained through practice, study or knowledge covering general truth of the operations of general laws especially, as obtained and tested through scientific methods concern with the physical world.
Science is a primarily tool for development of nations; this means the before any nation will develop, it must consider the learning and implementation of scientific and technological concepts.
Even though science has been one of the major parts of our educational policies, since time in memorial there are still lapses in teaching and learning of science this due to the approaches used by some of the science teachers in most science lessons.
SOME IMPORTANCE OF SCIENCE
i) It generates solutions for everyday life.
ii) It helps us to answer the great mysteries of the universe.
iii) It helps to make informed decisions,etc.
Science and Technology are related in the following ways:
i) Knowledge from science serves as a source for new technological possibilities.
ii) As a source of tools and techniques for more efficient engineering design and a knowledge base for evaluation of feasibility of designs.
iii) As research instrument, laboratory techniques and analytical methods used in research that eventually find their way into design or industrial practices, often through intermediate disciplines, etc.
Rectilinear propagation of light is one of the perceived most difficult topics in science today, thus application confuses learners. This is because the concept involves all order areas of life such as shadow formation, reflections and refraction of light, eclipse formation, arrangements of the pinhole box and so on.
However, based on the importance many researchers have tried to find remedy to pupil’s inability to understand the phenomena.
This research will review the meaning of the rectilinear propagation of light, the teaching techniques used, the step by step in teaching the topic as well as application of the rectilinear propagation of light.
MEANING OF RECTILINEAR PROPAGATION OF LIGHT
According to Abbey and Essial (2002) light travel within any uniform medium in a straight line this known as rectilinear propagation of light. Light travels in a straight line supports the theory that light emitted in packet of energy.
However some more refined experiment support the theory that light is transmitted in waves.
Nelcon and Parker (1970) held the view that rectilinear propagation of line can be observed if sunlight streaming through the window in the room.
It will be realized that the edge of the beam of light, and where the shadow begins are straight, this suggest that light travels in a straight line in this assumption, the shadow and the formation of eclipse can explain.
A shadow is an area of darkness caused by light being blocked by something or an object. Shadows are formed when an opaque material blocks the ray of light from reaching the surface (Cambridge English Dictionary ,2015)
An eclipse is an observation of light of the moon by the intervention of the earth between it and the sun(lunar eclipse) or observation of the light of the sun by the intervention of the moon between it and the point on the earth(solar eclipse) (Mariam Webster, (2015).
The phenomena that if a ray bulb is placed on sheet of every narrow beam of light with straight sharp edge are formed, it can therefore be said that light travels in a straight line and the principle is referred to as rectilinear propagation of light (Shepherd, 2003). In case the existence of shadows and the eclipse of the sun and the moon are further evidence phenomenon.
TEACHING TECHNIQUES
According to laud and Chales (2003) demonstration is the method in which the teacher displays certain objects and action in the class so as to teach a particular concept.
This help the learners to observe and practice what the teacher has with or without coaching. Demonstration method comes in two types that is Method demonstration and Result demonstration.
Farrat (2002) asserted that efficient learning of science depends on well-chosen and well managed activities in writing, drawing and speaking.
In the current trend in science education, activity method is the mode through which a child is helped to use his or her manipulative skills to learn and understand concept without difficulties (Majorie,2005). The activity oriented approach is child centered and involves experimental, project problem solving, guide and discovery methods.
However, the researcher tried using this approaches to improve upon the understanding of pupils on the rectilinear propagation of light to make teaching real.
STEPS IN RECTILINEAR PROPAGATION OF LIGHT
Adjei (2004) stated that to teach this topic, three pieces of cardboard screen with holes in the center are set in the straight line.
These cardboards are arranged by passing a string through the holes in a way that one can see through the holes. Light a candle and place it behind the first cardboard where the frame is in line with the hole.
A light is received in front of the last cardboard. Move the middle cardboard slightly and It will be observed that light has never appeared on the screen in front of the last cardboard.
Abbey and Essial (1990), has arranged three pieces of cardboard and punch a hole of about one millimeter in diameter through the middle. Arrange them to stand about 50 millimeters apart and pass a string through them in alignment on the table and then remove the string. Place a lamp behind the first piece of cardboard.
Observe the lamp from behind the third cardboard (c), display (b) slightly out of the line with A and B. an observer at c cannot see the lamp at a. now how can the lamp at a be made visible from c.
According to Keith (2001) a simple pin-hole camera consists of a closed box with a screen at one end and a small pin-hole at the other end.
It uses the fact that light going in through the pin-hole travels in a straight line to the screen. The picture produced is called image. In pinhole camera the image produced is inverted, thus turns upside down, turn right of left.
Lewis and Fexcroft (2005) a pinhole camera can be made using a small rectangular cardboard box with a circular pinhole in one end about 4cm in diameter and a large rectangular hole at the other end. The circular pinhole camera is covered with a black sheet of paper in which hole can be made with pin.
The rectangular hole at the back is covered with a screen of special paper like grease proof paper which lets light pass through it. Set up a lamp. Make a single hole in the middle with a pin on the black paper.
Hold up the camera with the pinhole directed towards the lamp, look out the screen from behind the camera (the camera should be at least a diameter from the lamp). What you see on the screen is called the image and it’s turned upside down.
The image formed on the screen by light travelling from the window through the pinhole in a straight line and the image is said to be inverted.
Simpi and Asiedu (2007) arrange three cardboard with a pinhole in their middle in a straight line by passing a string through the hole.
Remove the string and place a source of light e.g.; electrical lamp behind the first cardboard. Cardboard b is displaced slightly so that the cardboard are no longer in a straight line.
It will be observed that light can be can be seen through the third cardboard. However on shifting one of the cardboards slightly, the light is out from reaching an observer behind the first cardboard.
APPLICATION OF RECTILINEAR PROPAGATION OF LIGHT
Adjei (2004) create a box with a pinhole on one side and the opposite side and painted the inside of the box black to avoid the reflected from outside.
He covered the pinhole with a shatter and when the shatter is removed to have an exposure, light from all points of a bright object travel in a straight line through a pinhole to form an inverted image on the screen.
He further explained that, when a much large hole is created, the image formed on the screen of the camera will appear blurred.
What happens in such a situation is that the larger the holes, acts as a group of tiny holes where every tiny hole is produces its own image which is bright but very blurred. Whitely (2005) one of the most obvious properties of light is that beams of light travels in a straight line.
Beams of sunlight passing through gaps in clouds and beams from sunlight, pocket touch or car head lamps, may all be observed to have straight boundaries’ illustrations that determines that light travels in a straight line. Each of the two sheets of cardboard pierced by a small hole and placed near a candle flame.
It will be found that the flame in visible through both the screens only if it is on a straight line which passes through the two holes. The direction to which the light is travelling is often refers to as rays.
Abbey and Essial (2004) stated that the operation of the pinhole camera depends on the facts that light travels in the straight line, the pinhole camera is a box there is painted black in the inside to prevent reflection from the sides. There is a hole at the front and a film is exposed when the shatter is removed or opened. The image formed is diminished and inverted.
The image is deeply focused if the hole is small like pinhole but small holes admits little lights, so the image is deem and needs long exposure to bring a strong image though Bright. The shape of the hole if it is small has no effect on the shape on the image.
SUMMARY
In conclusion, the review has shown that all the previous study on the concept of rectilinear propagation of light has individual perceptions though author talks about the subject, importance to the society and also its relation with technology.
Again authors express and stress on the importance of introducing or teaching a science concept with appropriate, concrete, manipulative or teaching and learning materials.
Adopting the outlined researchers teaching could make children to develop much interest in science. However due to the importance of rectilinear propagation of any light related concept there is the need for more research on the topic to find other possible ways to make peoples up and doing in science. These research will therefore go a long way to apply some of the suggestion in different content.
Back to Chapter One
Forward to Chapter Three
SOURCE: bbcpulse.com