Sometimes light behaves like a wave and sometimes light behaves like a particle.
- Diffraction – can be explained by considering light to be a wave.
- Photoelectric effect – can be explained by considering light to be a particle.
Therefore we use the concept of wave-particle duality when thinking about light.
The momentum of a particle can be calculated by multiplying it’s mass in kilograms (kg) by it’s velocity in metres per secons (m s-1). Momentum is measured in kilogram metres per second ( kg m s-1 )
momentum = mv
De Broglie wavelength
De Broglie suggested that all particles not just light exhibit wave-particle duality and therefore it would be possible to calculate the wavelength of particles (the De Brogiel wavelength).
- l = the de Broglie wavlength of the particle in metres (m)
- h = the Plank constant 6.63 x 10-34 J s
- m = mass of the particle in kilograms (kg)
- v = velocity of the particle in metres per second (m s-1)