The Human Eye and the colourful world

Parts of the Eye

10

This part of the eye controls the amount of light entering it.

Iris

20

This is the clear, dome-shaped surface that covers the front of the eye.

Cornea

30

This part adjusts the shape of the lens for focusing.

Ciliary Muscle

40

This part sends visual information to the brain.

Optic Nerve

50

Name the part of the eye responsible for maintaining intraocular pressure and describe its role.

Aqueous Humour

Functions

10

This function helps us see objects clearly at different distances.

Power of Accomodation

20

The eye forms an image on this light-sensitive layer

Retina

30

This fluid fills the space between the lens and the retina.

Viterous Humour

40

This happens when the eye lens becomes cloudy.

Cataract

50

The minimum distance at which the eye can focus clearly.

Near Point

Defects of Vision

10

This defect is also known as nearsightedness.

Myopia

20

This defect occurs when the eye cannot focus on near objects.

Hypermetropia

30

This condition makes it difficult to see both near and far objects due to aging.

Presbyopia

40

This lens is used to correct myopia

Concave

50

How the shape of the eyeball affects vision in myopia and hypermetropia.

In myopia, the eyeball is elongated, causing images to form in front of the retina. In hypermetropia, the eyeball is too short, causing images to form behind the retina.

Light Phenomena

10

This is the bending of light as it passes from one medium to another.

Refraction

20

This natural phenomenon occurs due to dispersion, refraction, and total internal reflection

Rainbow

30

This phenomenon causes stars to appear to twinkle

Atmospheric Refraction

40

This term describes the splitting of white light into its colors.

Dispersion

50

This phenomenon causes the sky to appear blue.

Scattering of Light

Numerical

10

A concave lens has a focal length of 50 cm. What is its power?

_-2D

20

A convex lens has a power of +4 D. What is the focal length in meters and cm?

+0.25 m or +25 cm

30

A myopic person has a far point of 2 m. What power of lens is required to correct his vision?

- 0.5D

40

A person is prescribed a lens of power +2.5 D. What is the focal length of the lens in centimeters? Also, identify the type of lens.

+40 cm (f = 100/2.5), and it is a convex lens.

50

A student uses a lens of focal length –25 cm to correct his vision.
a) What defect does the student have?
b) What is the power of the lens?
c) What is the nature of the lens?

a) Myopia
b) Power = 100/f = 100/(–25) = –4 D
c) Concave lens