Reflection and Refraction

This topic allowed us to have a more visual approach when learning and approaching the topic. Reflection and refraction is actually not that hard if the concepts are understood, and by carrying out practicals, it enhanced our visualization and understanding of the topic.

The first and only time I calculated the refractive index was during the test. And the calculator kept saying error. As it is the first time the refractive index was calculated, I had no idea what went wrong.  I had no choice but the make an intelligent guess of the answer. I had guessed the correct answer, but written “B” like a “D”. Moral of the story? Write properly ><

On top of that, I would like to comment that the practicals were aesthetically pleasing to the eye as well. When we are done with the practical, we would play around with the lighting and set up and snap random pictures. Playing with light can be much fun after all. Do view some of the random pictures taken:

The part on real images and virtual images was rather confusing to begin with, and the notes did not define it well enough. Checking the net was the next option and I managed to get a better definition and develop a better understanding of the difference between real images and virtual images. Actually, the net can be great source of information for us, but it depends whether we bother to check it out in the first place. Science is a subject that involves a lot of information and knowledge that cannot be covered with only our notes, there has to be an element of self-learning in it. Maybe in the near future, we may rely a lot on our computer…

External Reading:

Well, who was the one which discovered the laws of reflection? Just a check on WikiAnswers and YahooAnswers, the answer is Rene Descartes. However, the discovery of the laws of reflection may date back even further- to the days of Euclid. 

Euclid states that:

1) Light travels in straight lines and will reflect from a smooth surface at the same angle with which it impacted it

2) Light is reflected in the same way that a ball would bounce off of a frictionless surface. Euclid claimed that light travels in rays that are discrete, like atoms but appear continuous, like waves, because they move so quickly 

If Euclid was the first one to make the discovery, then why do many think that it was Descartes who made the discovery? One possible explanation is that Descartes published an essay on optics and mentioned this law. In short, Descartes was the first person to publish on the laws of reflection, and most adopt his writing as the most plausible interpretation of the laws of reflection. 

Euclid

Rene Descartes 

Also, another thing I observed was that a particular scientific theory or law may go through many changes and improvements as time goes by. Take the laws of refraction for example. 

1) Greek astronomer Hipparchus compiled the first documented table of sine function before 125 BC. His work was referenced by Ptolemy over two hundred and fifty years later and so it is not known why he did not derive the sine law of refraction himself.

2) Ptolemy first tried to experimentally derive the law of refraction in the 2nd century AD

3) In 984, Ibn Sahl, a mathematician from Baghdad, discovered the law of refraction that Ptolemy had been searching for. Sahl showed that the angle of incidence is related to the angle of refraction using the law of sines 

4) The sine wave could not be represented graphically until the invention of the Cartesian co-ordinate system by French Philosopher Rene Descartes and French mathematician Pierre de Fermat in 1637.

5) The sine law of refraction, first discovered by Ibn Sahl in 984, was rediscovered by Dutch mathematician Willebrord Snellius in 1621. Snellius' theory was not published in his lifetime 

What can we tell from this? A particular scientific theory may need to be refined or improved as times go by. Issac Newton once said: If I have seen further it is by standing on the shoulders of giants. Perhaps without Ibn Sahl  or Snellius, would not have been able to publish the laws of reflection (or refraction). Scientific achievement should always be viewed as a collaborative effort rather than an individual effort. The scientist of today must thank their predecessors for making discoveries in which they were able to work upon or improve it. Imagine if fire was not invented...