Our laboratory practicals for term 3 is all about light. This includes reflection, refraction, lens and colours.The 1st practical done was on reflection, determining the law of reflection: angle of incidence= angle of reflection. There are 2 parts for our practical, 1 is for plane mirror and the other is for curved mirror.
These are the steps to prepare the trace sheet.
1. Place the mirror at the centre of a piece of white paper (portrait). Using a pencil, trace the front of the mirror and label it AB.
2. Remove the mirror and mark the mid-point of the line AB. Using a ruler, construct a dotted line at the mid-point such that it is perpendicular to line AB.
3. Using a protractor, measure for the angle of incidence - 20 degree. Draw the incident ray for angle of incidence = 20 degree. Label the ray as I20. Repeat the measurement for other angles of incidence and construct I30, I40, I50, I60, I70 respectively.
These are the procedures to prepare the practical.
1. Set up the laser unit in the laser bench. The laser module should be plugged into the lower socket. To activate the laser beam, turn the screw on the central module.
2. Lay the trace sheet on the board that is propped up with a door wedge inside the laser bench. Make sure the laser path goes across the mid-point of line AB.
3. Position the front of the mirror along the line Ab and rotate the setup such that the laser path is in line with I20 as shown in the diagram.
4. Using the card to help trace the laser path away from the mirror, mark out two points far apart along the path. Remove the mirror and draw a straight line passing through the two points and the mid-point of AB. Label the reflected ray I20.
5. Measure the angle of reflection and record it in the table below.
6. Repeat the experiment with other values of angle of incidence.
I followed all the steps and I found out that the angle of incidence when hit a mirror and reflects, the angle of reflection is plus minus 1 away from the angle of incidence. Thus, from here, I can conclude that angle of incidence actually does match with angle of reflection but due to human error, the results are off by a bit. The same thing was done on curved mirror and the results were also the same, thus, the law of reflection applies even to curve surface. The extra job needed to do was to draw a tangent.
We moved on with mirror image. We are supposed to observe the different characteristics of image formed in plane mirror. The results are that the image has the same size as the object, same orientation, laterally inverted, virtual and it is the same distance away from the mirror as the object to the mirror. I cannot believe that an image of myself in the mirror has so many characteristics and I went home and literally try it again. I got the same results, my image has all the characteristics as the results above. We also tried out with concave and convex mirrors. The results received is totally different from the plane mirror. For concave mirror, when I am close to the mirror, my image is upright and magnified, when at focal point, my image disappear and further away from focal point, my image is inverted but still magnified. For convex mirror, there is no changes when I move nearer or further away and my image is always upright and diminished. I don't understand the logic behind it but my science teacher say she will explain more when it comes to lens.
The next practical done was on refraction. For almost the entire lab lesson, I wasn't doing according to the practical and was exploring refraction on my own. I was playing with the translucent blocks given to us and trying to know what refraction was all about. When I comes to something I feel strange or I do not understand the logic, I will approach my science teacher and she will explain everything. Although I have not done my practical, but I managed to understand how a light ray bends as it pass through a different medium. Also, I was introduced on critical angle and total internal reflection. These 2 components are slightly more complicated as you must know how a light ray actually "moves" from object to object or from medium to medium. It is actually very easy to understand if you know refraction well. It is just what happened when angle of refraction is at 90 degrees or more.
Lens is the the crazy topic in our last practical. I only could catch a bit of what my teacher talks about lens and I shall wait for term 4 when she fully explain what is lens. There are in total of 6 cases to know and I and quite confuse with it. I am sure I can understand after my science teacher explains more about it :D
These are the steps to prepare the trace sheet.
1. Place the mirror at the centre of a piece of white paper (portrait). Using a pencil, trace the front of the mirror and label it AB.
2. Remove the mirror and mark the mid-point of the line AB. Using a ruler, construct a dotted line at the mid-point such that it is perpendicular to line AB.
3. Using a protractor, measure for the angle of incidence - 20 degree. Draw the incident ray for angle of incidence = 20 degree. Label the ray as I20. Repeat the measurement for other angles of incidence and construct I30, I40, I50, I60, I70 respectively.
These are the procedures to prepare the practical.
1. Set up the laser unit in the laser bench. The laser module should be plugged into the lower socket. To activate the laser beam, turn the screw on the central module.
2. Lay the trace sheet on the board that is propped up with a door wedge inside the laser bench. Make sure the laser path goes across the mid-point of line AB.
3. Position the front of the mirror along the line Ab and rotate the setup such that the laser path is in line with I20 as shown in the diagram.
4. Using the card to help trace the laser path away from the mirror, mark out two points far apart along the path. Remove the mirror and draw a straight line passing through the two points and the mid-point of AB. Label the reflected ray I20.
5. Measure the angle of reflection and record it in the table below.
6. Repeat the experiment with other values of angle of incidence.
I followed all the steps and I found out that the angle of incidence when hit a mirror and reflects, the angle of reflection is plus minus 1 away from the angle of incidence. Thus, from here, I can conclude that angle of incidence actually does match with angle of reflection but due to human error, the results are off by a bit. The same thing was done on curved mirror and the results were also the same, thus, the law of reflection applies even to curve surface. The extra job needed to do was to draw a tangent.
We moved on with mirror image. We are supposed to observe the different characteristics of image formed in plane mirror. The results are that the image has the same size as the object, same orientation, laterally inverted, virtual and it is the same distance away from the mirror as the object to the mirror. I cannot believe that an image of myself in the mirror has so many characteristics and I went home and literally try it again. I got the same results, my image has all the characteristics as the results above. We also tried out with concave and convex mirrors. The results received is totally different from the plane mirror. For concave mirror, when I am close to the mirror, my image is upright and magnified, when at focal point, my image disappear and further away from focal point, my image is inverted but still magnified. For convex mirror, there is no changes when I move nearer or further away and my image is always upright and diminished. I don't understand the logic behind it but my science teacher say she will explain more when it comes to lens.
The next practical done was on refraction. For almost the entire lab lesson, I wasn't doing according to the practical and was exploring refraction on my own. I was playing with the translucent blocks given to us and trying to know what refraction was all about. When I comes to something I feel strange or I do not understand the logic, I will approach my science teacher and she will explain everything. Although I have not done my practical, but I managed to understand how a light ray bends as it pass through a different medium. Also, I was introduced on critical angle and total internal reflection. These 2 components are slightly more complicated as you must know how a light ray actually "moves" from object to object or from medium to medium. It is actually very easy to understand if you know refraction well. It is just what happened when angle of refraction is at 90 degrees or more.
Lens is the the crazy topic in our last practical. I only could catch a bit of what my teacher talks about lens and I shall wait for term 4 when she fully explain what is lens. There are in total of 6 cases to know and I and quite confuse with it. I am sure I can understand after my science teacher explains more about it :D