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In an experiment to verify Snell’s law, a student recorded the following data - Leaving Cert Physics - Question 3 - 2010
Question 3
In an experiment to verify Snell’s law, a student recorded the following data. | i /° | 30 | 40 | 50 | 55 | 60 | 65 | 70 | |-------|----|----|----|----|----|----|-... show full transcript
Worked Solution & Example Answer:In an experiment to verify Snell’s law, a student recorded the following data - Leaving Cert Physics - Question 3 - 2010
Step 1
Draw a labelled diagram of the apparatus used. On your diagram, indicate an angle i and its corresponding angle r.
Answer
- Draw a rectangle to represent the glass block, positioning it horizontally in the center of the diagram.
- Indicate an incident ray approaching the glass block from the left at an angle i. Use a straight line with an arrow pointing towards the block.
- Draw a normal line (perpendicular) at the point where the incident ray strikes the glass block.
- Show the refracted ray bending into the glass block, labelled as the refracted ray. The refracted ray should be drawn continuing into the glass block at an angle r.
- Label the angles on your diagram: angle i (the incident angle) and angle r (the refracted angle). Make sure to clearly write these labels next to the respective angles.
Step 2
Using the recorded data, draw a suitable graph and explain how your graph verifies Snell’s law.
Answer
- Create a scatter plot with sin(i) on the x-axis and sin(r) on the y-axis using the provided data.
- Plot the points corresponding to the pairs of sin(i) and sin(r) from the data table. This means using the values calculated in the table for sin(i) and sin(r) for each angle.
- Connect the plotted points with a straight line to indicate the relationship. A linear trend shows that as sin(i) increases, sin(r) also increases proportionally.
- To verify Snell's Law, state that the graph should ideally show that sin(i) is directly proportional to sin(r), confirming that Snell’s law holds: .
Step 3
Using your graph, calculate the refractive index of the substance used in the experiment.
Answer
- The refractive index n can be calculated using the formula:
- Use the values of sin(i) and sin(r) from your graph for a pair of recorded angles. For example, for i = 30° and r = 19°:
- Repeat this process with different angle pairs to ensure consistency, and report the average refractive index based on your calculations.
Step 4
The student did not record any values of the angle i below 30°. Give two reasons why.
Answer
- To reduce the percentage error: At lower angles, the precision of the measurement could be hampered due to the angular resolution limits of the equipment used.
- It can be difficult to accurately measure the refracted angle r when the incident angle i is below 30°, as the angles may not yield clear readings due to refraction's properties near the threshold of total internal reflection.