Speed of light

Item Code: SK077

Working and Principle :

The LASER beam from the Transmitter strikes the Beam Splitter to split the beam in two perpendicular directions. The first beam is transmitted through Transmitter directly and is received in first channel of the receiver. The second perpendicular beam from Beam Splitter travels a larger distance by being reflected back from a mirror placed about 5 meter or more and is received in second channel of the receiver.
In the present setup, the time difference between the two peaks of received LASER signals can be observed on a oscilloscope (>40MHz) and can be used to calculate the Speed of Light.




  • 1MHz internal modulation frequency.
  • Dual Photo Detector built-in single assembly.
  • Transmitter and Receiver with Low Power Consumption (5V DC, 1A).

  • To determine the Speed of Light in air.
  • Laser transmitter : Peak wavelength 635nm, Modulation frequency 1MHz, output BNC (F), voltage 5V DC, current 250mA, optical power 0.4 to 0.8mW, Laser Class II, operating temp. 0 to 40°C, storage temp. -10 to 50°C
  • Laser receiver : Photo detector (BPW34) Silicon PIN Photodiode, Reverse voltage 32V, Max. current 30nA, Peak wavelength 850nm, Rise time 20ns, Fall time 20ns, Angle 60°, Photo current 80μA, Power dissipation 150mW, Responsivity 0.62A/W, Radiant sensitive area 2.65 x 2.65mm (LxW), output BNC (F), Operating voltage : 5V DC
  • Beam splitter : Size 50x50x10mm, R:T 50:50%, Surface λ/5 Mounting rod 10mm diameter
  • Reflecting mirror : Size 50x50x6mm, Surface λ/5, Mounting Rod 10mm diameter
  • 1 LASER Transmitter Module
  • 1 Receiver Module
  • 2 Power Adaptor 5V
  • 1 Beam Splitter
  • 2 Convex Lens f = 50mm
  • 5 Cylindrical Base
  • 1 Reflecting Mirror in Mount
  • 1 ‘A’ Base
  • 1 Support Rod
  • 2 BNC to BNC Cable
  • 1 Oscilloscope >40MHz (Not Supplied)
  • 1 Measuring tape (3m)
  • 1 Boss Head
  • Speed of light.
  • Internal modulation.
  • Laser beam.
  • Peak difference.
  • Path difference.