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I have a question regarding the working of optical discs. We know that Blu-ray disc stores more data than DVD. There are two reasons for that:

  1. The pits are smaller
  2. The wavelength of blue light is smaller than red light (which is used to read DVD)

Now I'm unable to understand how does smaller wavelength increase the storage capacity. Is it related to energy as the laser of a shorter wavelength is more energetic?

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Nothing to do with power instead the ability to focus a coherent beam is limited by diffraction and the size of a diffraction limited spot is proportional to the wavelength and inversely proportional to the diameter of the lens; the angular size of the beam $\propto \frac{\lambda}{D}$

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