The Physiology of the Eye and Underwater Vision

Flashcards covering the anatomy of the eye, the process of vision, the physics of refraction in air and water, and the effects of depth on light and color.

How much of the information we receive about the world is processed visually?

More than $75\%$

According to the transcript, through which four parts of the eye does light enter to reach the retina?

The lens, cornea, aqueous humour, and vitreous humour

What is the function of the cornea?

It is the clear front ‘window’ of the eye with a dense leathery wall that allows light to enter.

What is the lens and what is its primary function?

It is a clear specialised protein structure which helps focus light onto the retina and adjusts focusing power.

What is the role of the Vitreous Gel?

It is a clear, firm jelly that forms the main bulk of the eye and helps support the internal structure.

How does the Iris function within the eye?

It acts as a diaphragm or circular shutter to control the amount of light entering and gives the eye its colour.

What does the Retina consist of and what does it contain?

It consists of finely layered nerve tissue and contains photoreceptors which are light sensitive cells.

What is the Optic Nerve?

A bundle of nerve fibres from the retina that takes impulses to the brain to allow us to see.

What is the purpose of the Ciliary muscles?

They change the shape of the lens to allow for clear fine focusing.

What is the function of the aqueous humour?

It is the fluid that gives the eye its shape; without it, the eye would not be round.

What is the Sclera?

The white of the eye that surrounds the eye and aids in its shape.

Where does a blind spot form in the eye and why?

It forms where the optic nerve leaves the retina because there are no photoreceptors in that location.

Why does the initial image that enters the eye appear upside down?

Because of the refraction of light through the lens, which is Convex.

How is 'Refraction' defined in the context of light?

The bending of light due to the change in the speed of light as it travels through different mediums.

What happens when light rays pass from water to air at the face mask?

The light bends Away from the surface of the face mask.

Why is vision blurred when diving without a mask?

The cornea no longer refracts the light properly because the density of water and the eye is similar, causing the focal plane to lie behind the retina.

As depth increases, what happens to the visibility and intensity of colour?

The range of visibility and intensity of colour decreases as absorption increases.

Which colour in the light spectrum is one of the first to be absorbed underwater?

Red

Compare the diffusion of long wavelengths and short wavelengths underwater.

Longer wavelengths (red) diffuse more easily compared to short wavelengths (purple).

How deep can light typically penetrate the ocean?

$$200\,\text{meters}$$

According to the percentage chart, at what depth is Green light at $12.5\%$ intensity?

$$30\,m$$

What is the intensity percentage of Blue light at $60\,m$?

$$6.25\%$$

How does a dive mask help the eye focus underwater?

It traps a layer of air between the eyes and water, allowing the eye to refract light normally as it is adapted for an air gas medium.

What magnifying effect does a dive mask have on objects?

Objects appear closer and $1/3$ bigger due to refraction.