Question

The human eye forms the image of an object at its:
A. Cornea
B. Iris
C. Pupil
D. Retina

Answer 1

Hint: Cornea is a thin outermost layer of the eye, which helps in refracting the light into the eye. Pupil is the opening at the centre of the eye, which regulates the amount of light that should enter. Iris controls the size of the pupil. Retina is a light sensitive membrane.

Complete answer:
We humans can see objects because of our eyes, when the visible light enters our eyes. Let us understand how we are able to see the objects in front of us. For better visualisation, we have a diagram too.

The light from the object in front of us enters the eye through a thin layer called cornea. This layer (cornea) has a higher refractive index than air and therefore helps in refracting the light into the eye.
At the centre of the eye there is an opening called the pupil of the eye. Light enters the inside portion of the eye through the pupil. This means that the pupil maintains the amount of light that should enter our eye. Where the light is very bright, the pupil contracts and when there is very little light, the pupil expands, allowing more light to enter.
The size of the pupil is controlled by the iris of the eye. After passing through the pupil, the light passes through a convex lens, which converges the rays of light at a point on a light sensitive membrane called the retina. Thus, the image of the object in front of us is formed on the retina.
After this, the retina sends the message of the image to the brain through nerve impulses. Then the brain interprets the data and this way sees the objects.

Note:
The colour of the objects that we see depends on the wavelength of light emitted by the object. Light is a wave of different wavelengths and different bodies emit different wavelengths. Also, note that the image must be formed on the retina and not at any point that is not in the retina. If the image is not formed on the retina then we will not be able to see the objects clearly. This is what happens when people suffer from eye defects.