Required Practical 8 - Measure the frequency, wavelength and speed of waves in a ripple tank and waves in a solid and take appropriate measurements

Question 1

What is a ripple tank?

Answer 1

• a ripple tank is used to observe the features of water waves
• a ripple tank is a shallow tray of water
• in the water is a vibrating bar - the bar is connected to a power pack
• when the bar vibrates it creates waves across the surface of the water

Question 2

What happens when light shines through the water?

Answer 2

• when light shines through the water, it produces an image of the waves on the paper

Question 3

Method for measuring the frequency, wavelength and speed of waves in a ripple tank:

Answer 3

1. Record the waves using a mobile phones - allows us to play back recording at different speed or freeze the image
2. Measure wavelength of the waves using a ruler placed on the paper. Freeze the image of the waves and then measure the total of 10 wavelengths using a ruler. Divide this value by 10 to find the length of one wavelength.
3. To find the frequency use a timer to count the number of waves that pass a specific point in 10 seconds. Divide this time by 10 to get the frequency.
4. Calculate the wave speed of the waves using the formula: wave speed = frequency x wavelength.

OR

1. Select a wave a measure the time it takes to move the length of the tank using a timer.
2. Measure the length of the tank using a rules
3. Calculate waves peed of wave by using formula: speed = distance
4. May get slightly different results to first method due to measurement errors e.g. timing

Question 4

Possible errors that make the experiment (measuring the frequency, wavelength and speed of waves in a ripple tank) less repeatable:

Answer 4

• measurement errors like timing
• human errors like miscounting number of waves that pass a certain point

Question 5

Method for measuring the frequency, wavelength and speed of waves in a solid:

Answer 5

1. When you turn on the power, the string vibrates (difficult to see vibration)
2. At a certain frequency you get a standing wave due to an effect called resonance
3. Measure the wavelength of the standing wave using a ruler.
4. Measure the total length of the standing waves from the wooden bridge to the vibration generator
5. Divide the length measured by the number of waves to calculate the wavelength of one wave
6. Measure the frequency by reading it from the signal generator.
7. Calculate the speed of the wave using the formula: wave speed = frequency x wavelength

Question 6

Description of apparatus used for measuring the frequency, wavelength and speed of waves in a solid:

Answer 6

• string with one end attached to a vibration generator
• other end of string is a hanging mass to keep the string taut
• vibration generator attached to a signal generator
• signal generator allows us to change frequency of vibrations the string

Question 7

Where do you find standing waves?

Answer 7

in stringed musical instruments e.g. guitar

Question 8

Results for measuring the frequency, wavelength and speed of waves in a solid:

Answer 8

• wave speed is the same for different frequencies and wavelengths
• wave speed depends on the taughtness of the string and the mass / cm at the end of the string
  
  • wave speed does not depend on the frequency or wavelength

Question 9

What is the advantage of repeating a measurement and calculating a mean?

Answer 9

• reduces effect of random errors
• more accurate mean