Speed of light difference in the speeds of photons of different energies, confirming that Lorentz invariance is verified at least down to the scale of the Planck length ("l" = ≈ ) divided by 1.2. In a medium, light usually does not propagate at a speed equal to "c"; further, different types of light wave will travel at different speeds. The speed at which the individual crests and troughs of a plane wave (a wave filling the whole space, with only one frequency) propagate is called the phase velocity "v". An actual physical signal with a finite extent (a pulse of light) travels
In the Light of What We Know In the Light of What We Know In the Light of What We Know is the debut novel of Zia Haider Rahman. First published by Farrar, Straus and Giroux, the novel was released in the spring of 2014 to international critical acclaim and earned its author the James Tait Black Memorial Prize, Britain's oldest literary prize. and the inaugural International Ranald McDonald prize 2016. The novel has already been translated into Dutch, French and Portuguese and is to be translated into several other languages. Much of the novel is set during the war in Afghanistan at the beginning of the