❌ 8. Required Practical: Waves (P12) Flashcards
Aim Of This Practical
In this practical you are making observations to identify the suitability of apparatus to measure the frequency, wavelength, and speed of waves in a tray of water and take appropriate measurements.
In this required practical, you will measure the speed of waves passing through a liquid (water). This will allow you to evaluate the equipment used and decide whether it is suitable for the experiment.
Hypothesis for this experiment
In all, I believe that the deeper the water, the quicker the wave will travel across the tray, and the shallower the water, the slower the wave will travel across the water. This is because in shallower water, there will be more friction with the seabed leading the waves to travel in a slower fashion.
Health And Safety
- Be careful of any water spillages on the floor and ensure they are cleared up to avoud anyone slipping over and hurting themself.
- If any glass is smashed, make sure that it is cleared away to avoid causing any hazards.
Equipment for this RP
- Tray
- Water Tap
- Ruler
- Large Beaker/Bucket
- Stopwatch
- Table of Results
Method For This RP
- Firstly, get out the tray along with all of the other pieces of equipment.
- Fill the tray with water, until the water level reaches up to 5cm.
- Lift one half of the tray up, a set height (e.g 3cm) and drop it, creating a wave in the water.
- Once the wave hits the opposite side of the tray, start the stopwatch, and try to stop it when the wave hits the opposite side.
- Then record this result in the results table, and repeat until you get 2 concordant results for the 5cm height of water.
- Now drain out a centimeter of water and repeat steps 4-5.
- Carry on draining out the water after each height has been tested until you’ve finished the 1cm height.
- Make sure all the results are fully recorded.
What is The Independant Variable in this Experiment
The Independant Variable in this experiment is the height of the water that is in the tray. This is because it is the variable that his altered throughout the experiment to see the effect it has on the time.
What is The Dependant Variable in this Experiment
The Dependant Variable in this experiment is is the time it takes for the wave to travel from one side of the tray to another. This is because the dependant variable is the variable that is being tested and measured for
What are The Control Variables in this Experiment
The Control Variable in the experiment is the size and length of the tray, as well as the height that you lean and drop the tray on to get a wave. These are control variables because these are kept the same throughout the experiment to ensure thst it is kept as a fair test.
How to lay out the Results Table (and what it is meant to show)
The results table should have three main columns, the ‘Depth of Water (cm)’ on the left, ‘Time Taken (s)’ for the water to travel in the middle, and if you want to, you can include the ‘wave speed m/s)’ on the right hand side. Under ‘Time Taken (s)’ you can have 3 or 4 sub-columns for each measurement with an average of however many you do.
This table is meant to show that as the depth decrease, the time it takes for the wave to travel should increase, however, due to the bad suitability of the method and equipment, trend or pattern could really be made.
How To Find The Frequency, Wavelength, And Speed Of Waves (+Equation that links them)
Frequency, wavlength, and the speed of a wave can all be related in one single equation, which goes by the following:
v = f x λ (Speed of Wave (m/s) = Frequency (Hz) x Wavelength (m)
In the experiment, you can find out the Wavelength, by measuring the length of each of the waves from each other, and you can find out the frequency by using the equation below:
T = 1/f or f = 1/T (f = frequency (Hz), T = time (s)).
With the frequency and wavelength, you can find the speed of the wave through the equation at the top.
Is The Equipment Suitable?
Overall, I believe the equipment used for this experiment is not really suitable at all for this test. This is because there are many areas where you rely on the human eye, and human reactions to take recordings and measurements all in quick succession, which can lead to some unreliable and inaccurate results too.
To improve this experiment, higher quality of equipment is needed, including a motor (attached to a power supply), an oscillating dipper, a light, a shallow tank, and a large screen to put underneath, as well as a device to possibly record the waves in motion. This way, you have equipment that is going to help you be more accurate with the strength of the wave you create and how well you take down the results.
How would you set out the graph?
I would put the ‘Height of the Water (cm)’ on the Y-Axis and the ‘Time Taken for Wave to reach the other side (s)’ on the X-Axis.
However, due to the poor equipment/method used in the experiment the results are not very accurate and the graph doesn’t even have a correlation. The graph should show a negative correlation between height of water and time the waves take to travel, showing the shallower the water, the slower they travel.
What conclusion can be made from my results in terms of my hypothesis
Overall, the results obtianed from both the table and the graph were simply wrong in this experiment. This means my hypothesis (which is actually right according to the laws of physics and if the experiment was done properly) does not fit in with the results that were obtained by the recordings. This is because my hypothesis suggested that there would be a negative correlation between the height and time the wave travelled (the shallower the wave the slower the time), wheras the graph, if anything, shows more of a positive correlation.
Evaluation of how the experiment was and the reliability of the results
The results obtained from the equipment used in this experiment was very poor, inaccurate and lacked any precision either. This is due the fact that the results in the table had no kind of correlation, and when you excluded what seemed to be anomalies in the graph, it gave the opposite correlation to the one that you are meant to find in this experiment. This highlights that if better equipment and methodlogy was used, then far better results would’ve been achieved.
How did the experiment go and what needs to change
Overall, we don’t think the experiment went well. The results that we got were inconclusive and did not show a general trend that we expected. Our findings did not match our hypothesis - we believe this was due to multiple anomalous results which resulted in unreliable results - possibly due to the inaccuracies within the method. This included a lack of consistency when it comes to dropping the tray - any interference with the person dropping the tray is not mentioned or dealt with mechanically. Also, when measuring the time, the timing is based on the reaction time of the person and also their eyesight - doing this process mechanically would mean that we would get more accurate results and better reliability. In comparison to the experiment done by our compatriots, our results were inaccurate and did not follow a consistent trend.
