Eye Diagram - GCSE Biology

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Introduction

  • Our body has five basic sense organs, and the eye is one of them.
  • It has a layer known as the retina that contains receptor cells.
  • The receptor cells in the retina are of two types: Cones and Rods.
  • It is with the help of the eye that we can see various objects, colors, and lights.

Real-life uses:

Eye Diagram GCSE learning concept showing colour vision, focus target, and study symbol

Diagram of the Eye

Eye Diagram GCSE showing labelled cross section of the human eye including cornea, lens, retina, and optic nerve

Eye Parts and Functions

Eye Diagram GCSE background image used as a visual section divider for eye topic

Adaptation in the Eye

  • The process in which the retina and pupil adjust according to varying light intensities that fall on the eye is called Adaptation.
  • In Dim Light, the pupils dilate to allow more light to enter, and the rod cells in the retina become more active.
  • These adjustments enable correct vision in low light.
  • In Bright Light, the retina interprets high-intensity light and sends signals to the brain. The brain, in response, constricts the pupils.
  • With this, potential damage to the retina is prohibited.

showing how the pupil changes size in bright light and dim light

background image used as a section break in eye revision notes

Accommodation in the Eye

  • The natural ability of the eye to change its lens’s shape to adjust its focus so that objects at different distances can be seen clearly is called Accommodation.

How Does The Eye Focus on a Near Object?

  • To see a near-placed object clearly, the eye must increase its focusing power.
  • For this, the ciliary muscles contract, loosening up the suspensory ligaments.
  • This makes the lens fat and more curved.
  • Therefore, light rays refract more and focus on the retina.

Eye Diagram GCSE showing near point focusing and how the lens bends light rays

How Does The Eye Focus on a Distant Object?

  • To see a distant object clearly, the eye must reduce its focusing power.
  • For this, the ciliary muscles relax, tightening the suspensory ligaments.
  • This makes the lens thinner and less curved.
  • Thus, light rays refract less and focus on the retina.

Eye Diagram GCSE showing far point focusing and how the lens focuses light onto the retina

Eye Diagram GCSE background image used as a section divider for eye diagrams

Defects of the Eye

Myopia (Short-Sightedness)

  • Myopia (Short-sightedness) is the condition in which objects placed at a distance appear faded.
  • This happens because the rays of light focus before the retina.

Causes:

  • Lengthy eyeball or Extra-curved cornea.
  • The patients suffering from this condition are short-sighted or myopic.

Hyperopia/Hypermetropia (Long-Sightedness)

  • Hyperopia/Hypermetropia (Long-sightedness) is the condition in which objects placed nearby appear blurred.
  • This happens when the rays of light focus behind the retina.

Causes:

  • Small eyeball or less curved cornea.
  • The patients suffering from this condition are long-sighted or hyperopic or hypermetropic.

Eye Diagram GCSE showing myopia and hypermetropia with image formed in front of and behind the retina

Treating Eye Defects

  • Correction of Myopia is done with a diverging lens.
  • The rays of light are diverged so that after refraction from the eye lens, they focus on the retina, not in front of it.

showing correction of myopia using a diverging concave lens

  • Correction of Hyperopia is done with a converging lens.
  • The rays of light are converged so that after refraction from the eye lens, they focus on the retina, not behind it.

showing a convex lens focusing parallel light rays onto the retina

Frequently Asked Questions

Solution:

The main parts include: cornea, iris, pupil, lens, ciliary muscles, retina, and optic nerve.

Solution:

Adaptation is the adjustment in the eye as per varying light intensities.

Solution:

In dim light, the pupil widens so that more light can enter the eye.

Solution:

Accommodation is the process of changing the shape of the lens to focus on near or distant objects.

Solution:

Myopia is when distant objects appear blurry. It happens when the eyeball is too long or the lens is too curved.

Solution:

Hyperopia is when nearby objects appear faded. It happens when eyeball is too short or the lens is too flat.

Solution:

Muscles in the iris control and change the size of the pupil. It can make it smaller or bigger.

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