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Chapter 2 - notes

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Course

Sensation And Perception (PSYC 315)

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Academic year: 2021/2022
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Millersville University of Pennsylvania

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chapter 2

Class Psyc 315

Type Lecture

The Beginnings of Perception

Light and Focusing

Light: The Stimulus for Vision

The electromagnetic spectrum is a continuum of electromagnetic energy that is produces by electric charges and is radiated as waves. Wavelengths: the distance between the peaks of the electromagnetic waves Visible Light: The energy within the electromagnetic spectrum that humans can perceive. Photons: one photon is the smallest possible packet of light energy Light reflected from objects in the environment enters the eyes through the pupil and is focused by the cornea and lens to form sharp images of the objects on the retina, the network of neurons that covers the back of the eye and that contains the receptors for vision. These visual receptors, the rods and cones, contain light-sensitive chemical scaled visual pigments that react to light and trigger electrical signals. Signals from the receptors flow through the network of neurons that make up the retia and emerge from the back of the eye in the optic nerve, which conducts signals toward the brain. The cornea and lens at the front of the eye and the receptors and neurons in teh retina lining the back of the eye shape what we see by creating two transformations: 1, the transformation from light reflected from an object into an image o the objects, 2, the transformation from the image of the object into electrical signals.

Light Is Focused by the Eye

The cornea, the transparent covering of the front of the eye, accounts for about 80 percent of the eyes focusing power, but like the lenses in eyeglasses, it is fixed in lace so cant adjust its focus.

The lens, which supplies the remining 20 percent of the eye’s focusing power, can change its shape to adjust the eyes focus for objects located at different distances.

This change in shape is achieved by the action of ciliary muscles, which in crease the focusing power if the lens ( is ability to bend light) by increasing its curvature.

The adjustable lens, which controls a process called accommodation, comes to the rescue to help prevent blurring. Accommodation is the change in the lens’s shape that occurs when the ciliary muscles at the front of the eye tighten and increase the curvature of the lens so that it gets thicker.

Loss of Accommodation With Increasing Age

The distance at which your lens can no longer accommodate to bring close objects into focus is called the near point.

Myopia

Most of these people have myopia or nearsightedness, an inability to see distant objects clearly.

The problem can be caused by either of two factors: 1, refractive myopia, in which the cornea and/or the lens bends the light too much or 2, axial myopia, in which the eyeball is too long.

The distance at which light becomes focused on the retina is called the far point. When an object is at the far point, a person with myopia can see it clearly.

Although a person with myopia can see nearby objects clearly (which is why a myopia is called nearsighted)

Laser-assisted in situ keratomileusis (LASIK) eye surgery which you should not get until youre 25, can be used to correct myopia.

Hyperopia

  1. One small area, the fovea, contains only cones. When we look directly at an object, the objects image falls on the fovea.
  2. The peripheral retina, which includes all of the retina outside of the fovea, contains both rods and cones. It is important to notes that although the fovea has only cones, there are also many cones in the peripherial retina. The fovea is so small, that it contains only about 1 percent or 50,000, of the 6 million cones in the retina.
  3. The peripheral retina contains many more rods than cones because there are about 120 million rods and only 6 million cones in the retina.

Macular Degeneration: a condition that destroys the cone-rich fovea and a small area that surrounds it. (Macula is a term usually associated with medial practice that includes the fovea plus a small

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Chapter 2 - notes

Course: Sensation And Perception (PSYC 315)

11 Documents
Students shared 11 documents in this course

University: Millersville University of Pennsylvania

Was this document helpful?
chapter 2 1
chapter 2
Class Psyc 315
Type Lecture
The Beginnings of Perception
Light and Focusing
Light: The Stimulus for Vision
The electromagnetic spectrum is a continuum of electromagnetic energy that is
produces by electric charges and is radiated as waves.
Wavelengths: the distance between the peaks of the electromagnetic waves
Visible Light: The energy within the electromagnetic spectrum that humans can
perceive.
Photons: one photon is the smallest possible packet of light energy
Light reflected from objects in the environment enters the eyes through the pupil
and is focused by the cornea and lens to form sharp images of the objects on the
retina, the network of neurons that covers the back of the eye and that contains the
receptors for vision.
These visual receptors, the rods and cones, contain light-sensitive chemical scaled
visual pigments that react to light and trigger electrical signals.
Signals from the receptors flow through the network of neurons that make up the
retia and emerge from the back of the eye in the optic nerve, which conducts
signals toward the brain.
The cornea and lens at the front of the eye and the receptors and neurons in teh
retina lining the back of the eye shape what we see by creating two transformations:
1, the transformation from light reflected from an object into an image o the objects,
2, the transformation from the image of the object into electrical signals.

Students also viewed

Related documents