Question

When light enters the eye, most of the refraction occurs at the:
A) Eyes
B) Outer surface of cornea
C) Iris
D) Pupil

Answer 1

The most of the refraction occurs where the transition of medium has large difference of refractive index of both medium. Since the transition from air into the cornea is the largest change of index therefore most of the refraction occurs at the surface of cornea. The other parts of eyes have less change in index. So light suffers less refraction inside the eye.

Complete answer:
Most of the refraction occurs at the outer surface of cornea when light enters the eye. Refraction is defined as bending of light from its original path when light travels from one medium to another. Refraction also depends on the refractive index of the medium. More the difference in refractive index of two mediums, more will be the refraction. So when light enters the eye most difference in refractive index is present between the air and outer surface of cornea. Here maximum refraction occurs. Whereas the inner parts of the eye, the difference of refractive index is not much as compared to that of air.

Around 80% of total refraction occurs at the cornea and remaining 20% occurs inside the eye. Since it is a natural phenomena, refraction of light cannot be stopped. The eye is also filled with aqueous humor which also plays a vital role for refraction. There is another part in the eye which performs refraction is the lens. The lens converges light rays to retina to form an image. The amount of refraction here is still less than at the cornea.

Note: Refraction is most at the surfaces where difference between refractive index of both medium is more. For an eye air is the medium from where light enters our eyes. So the refractive index between air and eye is much more than the inside parts of an eye. Also iris, pupil etc. do not cause much refraction inside an eye.