The comfortable distance to read objects is 25 cm. Some persons can see objects close to them clearly, but cannot see distant objects so clearly. On the other hand some persons can not see objects close by clearly but they can see distant objects quite well. These are called Myopia and Hypermetropia respectively.

Nature has provided eyes with eyelids to prevent any object from entering into them. Eyelids also shut out light when not required.

It is the eye disease in which eye lens becomes opaque and eyesight becomes foggy. This disease is treated by removing the opaque lens and inserting a new artificial lens.

At the junction of the optic nerve and the retina, there are no rods and cones. Hence, no vision is possible at the spot. This spot is called blind spot.

Difference between regular and irregular reflection:

Convex lens is thicker in centre.

Yes.

As in this case, angle of incidence is zero degree, so after reflection, light beam returns at some path i.e., along normal.

In our eyes, convex lens is present.

The banana appears yellow because it reflects red and green light but absorbs blue light.

White light can be formed by mixing the primary colours red, green and blue.

Black objects appear black because they absorb all the colours, no light is reflected.

Tap water reflects the light into our eyes. As long as an object reflects light into our eyes, we can see it.

Image stays on retina for about 1/16th of a second.