Optics (Physics) Part-III

We see the world around us because of the way our eyes bend (refract) light. The refractive or bending power of the cornea and humor is constant. However, that of the lens can be changed by changing its shape.

That is by making it more or less convex so that light can be properly focused on the retina. The greater the lens convexity or bulge the more it bends the light. The flatter the lens, the less it bends that light.

The eye lens is composed of a fibrous, jelly-like material. Its curvature can be modified to some extent by the ciliary muscles. The change in the curvature of the eye lens can thus change its focal length.

When the muscles are relaxed, the lens becomes thin. Thus its focal length increases. This enables us to see distant objects clearly. When you are looking at objects closer to the eye, the ciliary muscles contract.

This increases the curvature of the eye lens. The eye lens then becomes thicker. Consequently, the focal length of the eye lens decreases. This enables us to see nearby objects clearly.

Head Mirror is mostly used by doctors for the examination of ear, nose, and throat. It comprises a circular concave mirror, with a small hole in the middle and is attached to a head-band. Hence statement (d) is not correct. Remaining statements are correct.

The normal human eye can focus a sharp image of an object on the eye if the object located anywhere from infinity to a certain point called the "Near point".

The minimum distance of an object from eye to have its clear image is called "least distance of distinct vision". It is about 25 cm for the normal eye and denoted by 'D'.

The normal human eye can focus a sharp image of an object on the eye if the object located anywhere from infinity to a certain point called the "Near point".

The minimum distance of an object from eye to have its clear image is called "least distance of distinct vision". It is about 25 cm for the normal eye and denoted by 'D'.

The normal human eye can focus a sharp image of an object on the eye if the object located anywhere from infinity to a certain point called the "Near point".

The minimum distance of an object from eye to have its clear image is called "least distance of distinct vision". It is about 25 cm for the normal eye and denoted by 'D'.

Dioptre is the unit of measurement for the refractive power of a lens. The power of a lens is defined as the reciprocal of its focal length in metres.

D = 1/f

where D is power of lens in dioptre and f is the focal length in metres. Converging lens has positive optical power and diverging lens has negative optical power.

Dioptre is the unit of measurement for the refractive power of a lens. The power of a lens is defined as the reciprocal of its focal length in metres.

D = 1/f

where D is power of lens in dioptre and f is the focal length in metres. Converging lens has positive optical power and diverging lens has negative optical power.

The power of the sunglass is 0 dioptre.