AimThis report seeks to describe the relationship between the incident angle

and refracted angle of a ray of light through two media, and it's link to refractive index using Snell's law.

IntroductionWhen a ray of light travels from one medium to another, it's velocity

changes, relative to the difference in refractive index (a measure of how fast light moves through a medium) between the two media. This change in velocity causes the ray's trajectory to be slightly altered, causing the ray to curve.

The magnitude of this curve can be used to determine the relative refractive indices of the media, by divising theratio of sin1 (the angle between the incident ray(P) and the normal), to sin2 (the angle betweenthe resultant ray (Q) and the normal) (fig. 1). Thisis known as Snell's law (fig. 2).

Figure 2, Snell's Law (wikipedia.org)

Figure 1 Refraction of a ray through two media (wikipedia.org)

ApparatusThe materials used in the following experiment were as such:

1 light box

1 glass block, with rounded edges

1 sheet paper

1 black pen

1 blue pen

1 ruler

1 scientific calculator

1 protractor

MethodologyA block of glass was placed upon a sheet of paper. The relevant sides

(those through which the light would pass) of the block were traced on to the paper.

Then, a beam of light from a lightbox was shined through the glass block. The approximate middle of the incident ray (P) and the reflected ray (R) were drawn in.

Next, the glass block was removed from the paper and a ruler was used to connect the intersections of rays P and R and the glass block, resulting in the resultant ray, Q.

A protractor was used to draw the Normal ray at a 90 angle to the boundary of the glass. The protractor was then used to measure 1 and 2.

Finally, a calculator was used to find the sines of the aforementioned angles. The numbers were then rounded to the nearest thousandth, and divided, resulting in the refractive index of the substance.

Results

21.5; .367 26; .438 36.5; .595 39; .629 48; .74315; .259 18; .309 23; .391 28.5; .477 32; .530

The mean of sinY divided by the mean of sinX results in a value of 1.410, the refractive index of the substance, according to the data taken.

DiscussionThe value produced by the experiment was 1.410. The accepted value

for the material, however, cannot be known as the type of glass was unspecified. The most common glasses are Soda-lime glass, Crown glass, and Flint glass, with refractive indices of 1.46, 1.52, and 1.62 respectively(wikipedia.org). Even without knowledge of the accuracy of the experiment, several factors likely decreased its accuracy.

The lightbox, for instance, produced a relatively broad beam of light, rather than a single ray as is used mathematically. A laser pointer, or thinner source of light could have been used instead.

In addition, the rounded edges of the glass block caused the refracted ray to start ~1 cm from the surface of the glass, further adding to error. Had the block been perfectly rectangular (or closer to it) the experiment's accuracy would have improved.

Using a protractor to measure the angles of the light also likely hinderedthe accuracy of the experiment. A digital protractor or computerized scanner would have improved the accuracy of the measurements.

ConclusionThe results of the experiment clearly displayed that, as stated in Snell's

law, as X (The independent variable, incident ray) increased, Y (The dependent variable, resultant ray) also increased, at a rate demonstrating the refractive index of the glass.

Part Ba) What are two technological developments that were necessary before digital storage on media such as Cds was possible?

Before digital storage on media such as Cds was possible, binary code would've had to have been invented, as well as computers to process it, otherwise the data would be unreadable.

b) How is sound recorded as a digital code?

An ADC (Analog-digital converter) samples sound thousands of times per second, where the amplitude of the sound waves is recorded digitally in binary.

c) Describe how digital information is stored on a CD

When digital information is stored on a CD, an infrared laser is used to make grooves on the surface of the CD. The binary-encoded data is recorded by the depth of the groove on the CD; a square, slightly deeper pit is equivalent to 1, with the representation of 0 being slightly less deep.

d) Describe how information read from the surface of a CD would be converted into a signal that can be used to produce sound from a loudspeaker.

When a CD is read, a laser/light sensor go along the groove of the CD and read the pits and high spots (physical representations of binary 1s and 0s)which are then converted back into an analog signal. The signal is then amplified and sent to the sound system.

e) List the energy changes from singer to burning the master disc for making Cds

The singer's vocal chords vibrate, producing sound waves (kinetic energy), which the microphone converts into an analog signal (electrical

energy). The analog signal is converted into a digital signal (electrical energy), which is then burned (light energy, thermal energy) onto a cd.

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Mark Latysh Snell's law - Wikipedia, the free encyclopedia. 2015. Snell's law - Wikipedia, the free

encyclopedia. [ONLINE] Available at:http://en.wikipedia.org/wiki/Snell%27s_law.[Accessed 21 April 2015].