Procedure:
- I folded the blank paper into four equal parts. Then drew two intersecting lines perpendicular to each other.
- Using the protractor I drew the angles of incidences or rays measuring 10°, 20°, 30°, 40°, 50° and 60°.
- Then I drew a semi-circle on the top of the intersection representing the flexi glass and placed the flexi glass over the semi-circle.
- Plugged in the ray box to a power source and using the single slit barrier, I placed the light ray along the normal to ensure that the light is not bent at this point.
- I then placed the ray box allowing the light ray travels along the 10° then marked the refracted light on the glass.
- And then repeated step 5 with 20°, 30°, 40°, 50° and 60°.
- After that, I drew rays from the marks of the refracted light on the glass to the center.
- Lastly measured and recorded the angles of refracted light on the table.
Safety Considerations:
- I worked on a neat and no other mess area.
- I placed the paper and the flexi glass on the center of lab bench so that the ray box or the glass would not fall during the entire investigation.
- I moved and held the ray box cautiously.
Observations:
Qualitative Observations:
- The light coming from the ray bow was bent toward the normal.
- The light from the ray box were not that thin as the lines I drawn.
Quantitative Observations:
* the actual observation is attached on the last page.
Sample Calculations:
n1 sinθ1 =n2 sinθ2 difference
n1= 1.0003 8° - 6.56 ° = 1.44
sinθ1= 10°
n2 = 1.52 Sinθi/ sinθr
sinθ2 =? 10°/ 6.56° = 1.25
sinθ2 = n1 sinθ1
_______
n2
= 1.0003 x sinθ10°
________________
1.52
sinθ = 0.1142
θ = 6.56 °
Analysis
b. When light travels from air into glass along the normal, there is no refraction occurs.
c. Rays must be shone at the center of the flat surface because if not, the light would be reflected more than it will refract.
d. The angle of refraction is smaller than the angle of incidence.
e. The ratio for all angles of incidence greater than zero was precise. They have close numerical values which only varies in hundredths.
f.
M = Y2- Y1/ X2 –X1
= 20-10/14-8
= 1.67, the slope of the line in the graph is 1.67
The slope of the line in the graph represents the ratio of angle of incidence and angle of refraction. The ratio of angle of incidence to angle of refraction is constant. As the angle of incidence increase, the angle of refraction will also increase by some factors.
Sources of error:
- Since the light ray from the ray box is kind of thick, it’s hard to make the light travel along the exact angle and it also hard to mark the refracted light. If this maybe happens, it will result to inaccurate value. In able to avoid this, make sure that when marking the refracted light should be the center of the ray.
- Another source of error that probably occurred is the incorrect measure of the angle the light from the ray box or the angle of incidence, if the angle of incidence is not accurate it will not corresponds on the expected angle of refraction.
Conclusion:
Snell’s law states that the sine angle of incidence is directly proportional to the sine angle of refraction. We can see in my data that this law is true. As the angle of incidence increase the angle of refraction also increases. There might be a little bit difference with my predicted and measured angle of refraction, probably it’s because I used the index of refraction of crown glass, where crown glass is more optically denser than plexiglass. As I researched the index of refraction, according to wikipedia the index is 1.4893-1.4899. If I use this value I would actually get a closer value.
