5. (a) Which colour of visible light has the longest wavelength? A blue B green C red D yellow (b) Some television remote controls use infrared radiation and other remote controls use radio waves - Edexcel - GCSE Physics Combined Science - Question 5 - 2019 - Paper 1

Infrared remote controls emit infrared radiation, which can be blocked by solid objects such as furniture because they do not have the ability to diffract around obstacles. This obstruction prevents the infrared signals from reaching the television. In contrast, radio waves have longer wavelengths and can diffract around obstacles, allowing a radio wave remote control to function even when there are obstructions in the way.

To measure the wavelength of the wave in Figure 4, observe the distance between two consecutive peaks (crests) of the wave. Based on the graph in Figure 4, the measured wavelength is 10 cm.

The cork moves up and down as the wave passes but does not move forward in the direction of wave travel. This motion is caused by the oscillation of the water surface, resulting in a vertical displacement while maintaining its horizontal position.

To calculate wave speed ( v) using the formula:

  $$v = \lambda \times f$$
  where 
  \(\lambda = 0.25 \text{ m}\) 
  and 
  \(f = 1.5 \text{ Hz}$$). Thus,
  
  $$v = 0.25 \text{ m} \times 1.5 \text{ Hz} = 0.375 \text{ m/s}$$.