Human Eye in Cross Section –

Photo-transduction takes place when rod and cone cells in the human eye convert their chemical response to light into electrical signals ready to input into the visual system.

Yes! The human retina inside the eyeball has a light-sensitive layer of neurons on its surface?

The blind spot in the human eye corresponds with the point in the retina where the optic nerve exits and the central artery enters the eyeball.

Yes! The optic nerve is composed of the axons of ganglion cells and transmits visual information assembled within the retina towards the geniculate nucleus and the visual cortex.

A neuron is a type of cell that transmits electrical impulses around the brain and other parts of the central nervous system.

Visual perception is the human ability to see and understand our surroundings by virtue of the sensitivity of our eyes to wavelengths of light across the entire visible spectrum, from red to violet.

• Visual perception is a complex process that relies on the intricate interaction between our eyes, the brain, and the interpretation of light signals. It enables us to perceive various visual attributes such as shapes, sizes, textures, depths, motions, and spatial relationships, all of which contribute to our comprehensive understanding and interpretation of the visual world around us.

A human observer is a person who engages in observation by watching things.

• In the presence of visible light, an observer perceives colour because the retina at the back of the human eye is sensitive to wavelengths of light that fall within the visible part of the electromagnetic spectrum.
• The visual experience of colour is associated with words such as red, blue, yellow, etc.
• The retina’s response to visible light can be described in terms of wavelength, frequency and brightness.
• Other properties of the world around us must be inferred from light patterns.
• An observation can take many forms such as:
  • Watching an ocean sunset or the sky at night.
  • Studying a baby’s face.
  • Exploring something that can’t be seen by collecting data from an instrument or machine.
  • Experimenting in a laboratory setting.

 

An object is a material thing that has mass and occupies space.

• An object, as a physical entity, can be defined by its mass and the space it occupies. Objects are characterized by properties such as size, shape, texture, and colour, all of which are perceptible through the senses.
• The perception of an object arises from the brain’s interpretation of sensory information, primarily from the light reflected or transmitted by the object. At a fundamental level, all objects are composed of atoms or molecules, which form the basic structure of matter. The arrangement and behaviour of these atoms and molecules determine the object’s physical and chemical properties.
• Light plays a critical role in how objects are seen. Different atoms and molecules interact with light based on their unique structures and how they combine to form compounds or mixtures. When light strikes an opaque object, its surface molecules largely determine how the light is absorbed, reflected, or scattered. By contrast, translucent and transparent objects allow light to pass through, leading to different optical effects.
• Additionally, surface finish influences how light interacts with an object. Smooth, polished surfaces reflect light in a more uniform manner, while rough, textured, or rippled surfaces cause light to scatter in multiple directions.

Optical illusions and other visual anomalies are caused by the way the human visual system processes information.

• Physical illusions: Physical illusions result from the limitations and assumptions of the human visual system when interpreting the external world.
• Physiological illusions: Physiological illusions are often connected with the different attributes of visual perception and occur when visual stimuli are beyond our brain’s processing ability.
• Cognitive illusions: Cognitive illusions result from the brain’s inability to correctly interpret visual information, leading to uncertainties or errors in perception.

Interneurons are a type of neuron found in the nervous system of animals, including humans, which play a role in processing and communicating information.

• Interneurons can be classified into different types based on their functions, such as local circuit interneurons and relay interneurons.
• Local circuit interneurons have short axons and form circuits with nearby neurons to analyse and process information locally.
• Relay interneurons have long axons and connect circuits of neurons in different regions of the central nervous system, enabling communication and integration of information.
• Interneurons can be further classified into sub-classes based on their neurotransmitter type, morphology, and connectivity.
• Interneurons serve as nodes within neural circuits, enabling communication and integration of sensory and motor information between the peripheral nervous system and the central nervous system.

Visible light refers to the range of wavelengths of electromagnetic radiation that is perceived as colour by human observers. While the range of visible light is generally considered to be 400-700 nm, the exact range of colours perceptible can vary slightly between individuals.

• Visible light is one form of electromagnetic radiation. Other forms of electromagnetic radiation include radio waves, microwaves, infrared, ultraviolet, X-rays, and gamma rays. Visible light ranges from approximately 400 nanometres (nm) for violet to 700 nm for red.
• A human observer perceives visible light as a combination of all the spectral colours between red and violet, as well as a vast range of other colours produced from the blending of different wavelengths in varying proportions.

• The observer effect is a principle of physics and states that any interaction between a particle and a measuring device will inevitably change the state of the particle. This is because the act of measurement itself imposes a disturbance on the particle’s wave function, which is the mathematical description of its state.
• The concept of observation refers to the act of engaging with an electron or other particle, achieved through measuring its position or momentum.
• In the context of quantum mechanics, observation isn’t a passive undertaking, observation actively alters a particle’s state.
• This means that any kind of interaction with an atom, or with one of its constituent particles, that provides insight into its state results in a change to that state. The act of observation is always intrusive and will always change the state of the object being observed.
• It can be challenging to reconcile this with our daily experience, where we believe we can observe things without inducing any change in them.