Sensation/Perception Batch 2 Exam 1

Light

A form of electromagnetic radiation produced by motion of electrically charged particles.

Dual particle/wave nature

The wave can be bent by lenses, and when light is a particle it can travel through a vacuum (no transmission medium needed).

Visible light spectrum

Forms a very small part of the electromagnetic spectrum, ranging from 380 nm to 740 nm.

Frequency/wavelength/energy relationship

Short wavelength = high frequency; Long wavelength = low frequency.

Wavelength/color relationship

Short wavelengths → purple/blue; Long wavelengths → red.

Optics

Without optics, light from everywhere would just hit the retina without forming an image.

Mere light detection vs. image-forming eyes

Noting the presence of light vs interpreting an image based on the way the light bounces off of it.

Cornea

Front, transparent surface of the eye that carries most of the eye's reflective power.

Aqueous humor

Watery fluid behind the cornea.

Iris/pupil

The small hole that lets light pass through to the retina.

Lens

Part of the eye that allows changing focus.

Retina

Area at the back that converts light into nerve signals.

Emmetropia

Proper vision, nothing wrong.

Myopia

Nearsightedness, can't see things far away (eye is too long, too powerful).

Hyperopia

Farsightedness, can't see things close up (eye is too short, not enough accommodation).

Astigmatism

One eye isn't corrected.

Presbyopia

Age-related eye deterioration.

Refractive Power

Adjusted through accommodation, the power needed to bring in light from nearby objects to view.

Diopters

A measure of the optical power of a lens or lens system.

Focal Length

Distance from center of lens to surface at which parallel rays are brought into focus.

Focal Distance

Distance from an object to the lens.

Phototransduction

The process of light passing through the retina and reaching towards the end to be turned into neural impulses/spikes.

On-Center Cells

Ganglion cells excited by light that falls in the center of the receptive fields and inhibited by light that falls in their surroundings.

Off-Center Cells

Ganglion cells that are inhibited when light falls in their center, and excited when it falls in their surroundings.

Pupil dilation/constriction

Pupil size (little= lets in less light, large= lets in more light).

Photopigment regeneration

Bleached photopigments have to be regenerated before they can be used again to absorb another photon.

Duplex retina

Rods and cones notably recover from bleaching at different rates.

Retinal convergence

Ganglion cells are encoded to be sensitive to light changes.

Retinal implants

Can be used to generate visual images in people who lost photoreceptors but retain ganglion and/or bipolar cells.