Compare and contrast the retina’s two photoreceptor cells, and explain the role rhodopsin plays in vision

Photoreceptors are responsible for visual phototransduction. They convert light into biological signals. In humans, rods, cone, and retinal ganglion cells are the 3 main photoreceptors.
Rods are narrow and are present throughout the retina. They are very sensitive, They can be triggered by a single photon also. They are responsible for the visuals we get in the low-light conditions.
Cons need a high number of photons, in order to produce signals. They are responsible for visualization of colors. 
Rhodopsin is the pigment molecule of the rod cells. It is very sensitive to the light, and enables visualization in dim lights.

Ok , hopefully this app

You're asking in the ap section, so i'll give the ap calculus-style answer. alternatively, you can find the vertex of the parabola and use the "y"-coordinate as the answer.

the maximum height can occur at a critical number, that is, a number  such that  .

the derivative of  can be calculated as follows:



find a value of  that is a zero of the derivative:


this is parabola that is opening downward; we can assume there is a maximum at  .

to find that maximum, calculate  .