Dependant: refractive index
Controlled: Weighing scale, beaker, amount of water poured into beaker, lamp
Planning B:
Material:
- 1 Weighing scale
- 1L beaker
- 3 different types of glass
(Glass1= Green Glass)(Glass2= Milky Glass)(Glass3= Transparent Glass)
- 1 Ruler
- 1 white light lamp
- Water (700ML) (every time volume of glass is measured)
Procedure:
- First of all, we need to find the density of the Glass.
- Fill a beaker with 700 ml of water.
- Place the first type of glass in the water. Record the volume, which is the amount of ml indicated on the beaker -700 ml. convert this to cm³ to get the volume.
- Now dry the glass and weigh it on the weighing scale.
- The density formula is: Density = mass/volume, now find the density using this formula.
- Repeat this procedure with the other types of glass.
- Now that the density has been found, find the refractive index.
- This is done by setting up the laboratory as follows:
- A lamp, enlightening the glass at an angle. (For this experiment, an angle of 135° was used). Normal = 135-90 = 45°
- An A4 paper under the glass, record the normal (line where light enters glass)
- Record where the light is exiting the glass on the paper.
- Measure the angle the light has come out from (angle between light exit and normal).
3. Now using the formula n= find n, the refractive index of all three glasses. Record the data in a table.
Data Collection, Processing and Presentation:
Density of glass:
Glass 1 (green glass):
Mass = 354.8 grams
Volume = 850ml – 700ml = 150 ml = 150 cm³
Density =
Glass 2 (milky glass):
Mass = 182.9 grams
Volume = 850ml – 700ml = 150 ml = 150 cm³
Density =
Glass 3 (transparent glass):
Mass = 187.0 grams
Volume = 850ml – 700ml = 150 ml = 150 cm³
Density =
C = 299,792,458 meters per second
There may be some error in the calculations; since the volume of the glass can only be measured to an extent (the beaker does not show small enough units to be 100% of the result). Furthermore, the weight of the glass is only measured to one decimal place, which means a very small range of error can occur. The angles may also be a bit off because they are not measured into decimal values.
Conclusion & Evaluation:
I can conclude the following:
Glass I
Density = High, Refractive Index = High, light Speed through glass = Slowest*
Glass II
Density = Medium, Refractive Index = Medium, Light Speed through glass = Slower**
Glass III
Density = Low, Refractive Index = low, Light Speed through glass = Slow***
* Slowest compared to real speed of light out of three glasses.
** Slower than glass 3, faster than glass 1.
*** Slower than real speed of light, but faster than light through glass 1 and glass 2.
When the light waves travel into the glass, its speed is decreased and its path is being bent towards the normal. Since the wave is slowing down, the wavelength is decreased.
Therefore, my hypothesis was right; density did affect the refractive index; the higher the density was the higher the refractive index. Thus, the speed of light through the object slowed down. This has also been proven by Snell’s Law.
