Calculating Frequency (OCR A Level Physics)

• Frequency (f) is defined by the equation:

• Where T is the time period, the time taken for one complete oscillation or cycle of the wave

Step 1: List the known quantities

• • Period, T = 0.28 ms = 0.28 × 10^-3 s

Step 2: Write down the frequency equation 

Step 3: Substitute in the values

f = 1 ÷ (0.28 × 10^-3) = 3571.4 = 3.57 kHz

• A Cathode-Ray Oscilloscope (CRO) is a laboratory instrument used to display, measure and analyse waveforms of electrical circuits
• The x-axis is the time-base and the y-axis is the voltage (or y-gain)
  • The time-base is important for calculating the frequency of the signal

Diagram of Cathode-Ray Oscilloscope display showing wavelength and time-base setting

• The frequency of a wave is determined from the time period of the wave
• The period can be determined from the time-base
  • This is how many seconds each division represents measured commonly in s div^-1 or s cm^-1

• Dividing the total time by the number of wavelengths will give a value for T
  • Use as many wavelengths shown on the screen as possible to reduce uncertainties

• The frequency is then determined using the equation: