physics - waves

Question 1

describe the steps of the practical that observes water waves in a ripple tank

Answer 1

• set up the ripple tank with a lamp above it and white card/paper below it
• switch on the motor attached to a wooden rod
• measure the wavelength of the waves being cast onto the card
• count the number of waves that pass a point in 10 seconds and calculate frequency
• calculate wavespeed

Question 2

how much water should you put in the ripple tank?

Answer 2

the ripple tank should be full to a depth of 5mm ~ if there is too much water the rod won’t produce clear waves and they will be less clearly projected onto the card below

Question 3

how should the wooden rod be set up in the ripple tank?

Answer 3

the rod should be placed into the tank so that it just touches the surface of the water

Question 4

how should you measure the wavelengths of the waves on the card?

Answer 4

• adjust the lamp position so that the waves are clearly projected onto the card
• using a metre rule, measure across as many waves as you can
• divide the distance by the number of waves measured across

Question 5

what units should your measured wavelength be in?

Answer 5

Metres, m

Question 6

why should you measure across more than one wave?

Answer 6

to reduce the uncertainty in the measurement and improve the accuracy of the value

Question 7

how do you measure the frequency of the waves on the card?

Answer 7

• count the number of waves to pass a point in 10 seconds
• divide the number by 10 to produce a frequency of Hz

Question 8

what equation is used to calculate wave speed?

Answer 8

wave speed = frequency X wavelength

Question 9

when the frequency is in Hertz and the wavelength is in metres, what is the unit for wave speed?

Answer 9

m/s
metres per second

Question 10

what are the steps for the practical where you can observe wave in a solid?

Answer 10

• attach a piece of string to a vibration generator at one end and to a mass hanger suspended over a pulley at the other
• place the wooden bridge under the string before it reaches the pulley
• start the generator and alter the tension and bridge until it looks like the wave isn’t moving
• measure the wavelength, record the frequency
• calculate the wavespeed

Question 11

how to measure the wavelength?

Answer 11

• use a metre ruler and measure across as many loops as possible
• each loop is a half wavelength
• divide the distance by the number of loops and multiply by 2 to get the wavelength

Question 12

what value is used for the frequency?

Answer 12

the value should be taken from the frequency generator settings