The lens.
The CCD is the part of the camera that changes the light that enters the camera into a digital signal that is then saved on the memory card. You can think of it as where the film would be in a regular 35mm film camera.
When you click the camera the shutter behind the lens of the camera opens briefly and lets in the light on to the film. I am no specialist and this is what I learnt in school.
The functional opening is the aperture, the opening that controls the amount of light that hits the photosensitive surface. You may have a camera with interchangeable lenses that screw into and out of the camera's body. The opening into which the lens is screwed is not the aperture.
The pupil is the center round black part of the eye. This is where the light enters into the retina. The human pupil works much like the aperture of a camera.
The energy that enters any kind of camera through the lens is called light.
The image formed on the screen of the pinhole camera is inverted because the aperture, which is a small hole, bends the light that enters the camera. This basically shows that light travels in straight line.
The shutter.
aperture is the amount of light which enters the camera. lower number the bigger hole ad the bigger hole is good for low light.
the iris
The setting which dictates the amount of light that enters the lens. f-stop...f-1.4
The Shutter.
This part is called a Lens, on the camera and the glasses the are made of either optical glass or optical plastic, in the eye the lens in an organic material. Lens allow light to enter the camera, eye or glasses, and focuses that light on a surface such as the camera's film, the eye's retina, and the glasses wearer's eyes.