Rods are more sensitive to light than cones because
- their photochemical pigment of rods responds to very low light intensities.
- Numerous rods make synaptic contact with a single bipolar neuron which in turn connects with cell body of a single optical nerve fibre. A phenomenon called Retinal convergence. Retinal convergence increases the sensitivity of the eye because simultaneous excitation of a number of rods is more likely to generate an impulse in the optical nerve than excitation of a single rod would not.
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