Images are focused by the lens onto the retina which is a face at the back of the eye upon which light sensitive cells (rods and cones) convert the incident light into electrical signals that are transmitted to the brain.
The fovea is a pit directly behind the lens on the retina that contains a concentration of light sensitive, closely packed cones (colour sensitive cells) and is responsible for sharp central vision.
Answer : The circumference of circle is, 94.2 cm
Explanation :
Formula used for circumference of circle is:
Circumference of circle = 
where,
r = radius of circle
Given:
Diameter of circle = 30 cm
Radius of circle = 
Now we have to determine the circumference of circle.
Circumference of circle = 
Circumference of circle = 
Circumference of circle = 94.2 cm
Therefore, the circumference of circle is, 94.2 cm