Lesson 3: RP: Speed of waves in solids/ liquids

Question 1

How do you work out the wavelength of the waves on the ripple tank?

Answer 1

• The water waves are reflected on a piece of paper (as light is shone on the water.)
• Freeze the image of the waves by taking a picture.
• Measure the distance of 10 waves using a ruler.
• Calculate the wavelength of 1 wave by doing the distance of 10 waves/10

Question 2

How do you calculate the frequency of water waves in a ripple tank?

Answer 2

• Record a video of the waves w/ a pencil on a certain point of the paper (fixed point.)
• From the video, count the number of waves that pass the pencil (the fixed point) in 10 seconds.
• Divide the number of waves by 10 to calculate the number of waves that pass a fixed point EACH SECOND.

Question 3

What is another way of calculating the wave- speed of water waves on ripple tank other than just using the equation?

Answer 3

• Select a wave and measure the time it takes for the wave to move the length of the tank.
• Calculate the speed of the wave by dividing distance travelled “by the wave” by time taken.

Question 4

Why do we use a mass when investigating the wave- speed of waves in a solid?

Answer 4

• To make the string taut so that the string vibrates when we turn on the vibration generator.

Question 5

What changes the frequency of the waves in the string?

Answer 5

• The signal generator.

Question 6

How do we change the wavelength of waves on the string?

Answer 6

• Increase frequency to decrease the wavelength.

Question 7

How do you measure the wavelength of the waves on the string?

Answer 7

• Use a ruler.
• Measure the length across as many half wavelengths as possible.
• Divide the total length (of the half waves) by the number of half waves. Multiply this number by 2 to give you the wavelength.

Question 8

What equation do we use to measure the wave- speed of the waves on a string?

Answer 8

wave- speed = frequency x wavelength.

Question 9

Does the wave- speed of the waves on the string change when you decrease the wavelength/ increase the frequency?

Answer 9

• No. The wave- speed remains the same.
• The wave- speed depends on the taugtness of the string.