RP

• Using a ripple tank to measure the wavelength, frequency, and speed of water waves

  Place a ruler on the paper, freeze the image of the waves, measure the distance between one wave and 10 waves further, divide by 10 to find one wavelength. To find the frequency, place a timer next to the paper, count the number of waves passing a point in 10 seconds, divide by 10. Calculate the wave speed by multiplying the frequency by the wavelength. Another method is to measure the time it takes for a wave to move the length of the tank and calculate the speed by dividing the distance traveled by the time taken
• Ripple tank

  • Used to observe the features of water waves, consists of a shallow tray of water with a vibrating bar connected to a power pack, creates waves across the surface of the water, produces an image of the waves on a sheet of white paper below the tank
• Record the waves using a mobile phone

  • Allows playback at different speeds or freezing the image completely
• Frequency is the number of waves passing a point each second
• Wavelength is measured by placing a ruler on the paper, freezing the image, and measuring the distance between one wave and 10 waves further
• Frequency can be found by counting the number of waves passing a point in 10 seconds and dividing by 10
• Wave speed is calculated by multiplying the frequency by the wavelength
• Another method to determine wave speed is by measuring the time it takes for a wave to move the length of the tank and calculating the speed by dividing the distance traveled by the time taken
• Measuring wavelength, frequency, and speed of waves in a solid

  Use a string attached to a vibration generator with a hanging mass to create standing waves. Measure the total length of the standing wave to calculate wavelength. Use the wave equation (speed = frequency x wavelength) to calculate the wave speed
• Standing waves are found in stringed musical instruments like a guitar
• Standing waves are due to an effect called resonance
• Calculating wavelength of a standing wave

  Divide the total length by the number of half wave lengths and then multiply by 2
• Wave speed does not depend on the frequency or wavelength, but on the tautness of the string and the mass per centimeter
• Factors affecting wave speed

  • Tautness of the string
  • Mass per centimeter
• Calculating wave speed

  Multiply the frequency by the wavelength using the wave equation (speed = frequency x wavelength)
• Investigating how much infrared radiation is absorbed or radiated by different surfaces

  Fill Lesley's cube with hot water, point an infrared detector at each of the four surfaces, record the amount of infrared emitted, keep the same distance between the Lesley's cube and the infrared detector for repeatability
• Lesley's cube surfaces

  • Shiny metallic surface
  • White surface
  • Shiny black surface
  • Matte black surface
• Matte black surface emits the most infrared radiation


  Followed by shiny black surface, white surface, and shiny metallic surface emitting the least infrared radiation
• Measuring the absorbance of infrared by different surfaces

  Use an infrared heater with two metal plates painted with shiny metallic paint and matte black paint, attach a drawn pin with Vaseline on each plate, switch on the heater and time the temperature increase until the drawn pin falls off, observe that the drawn pin falls off the matte black plate first indicating higher absorbance of infrared compared to shiny metallic surfaces
• Matte black surfaces absorb more infrared than shiny metallic surfaces


  Infrared tends to be reflected from shiny metallic surfaces
• THE LESLIE CUBE

  The independent variable is the colour of the surface. The dependent variable is the reading on the infra-red detector.

  The distance between the surface and the detector is a control variable.