Light

There are two laws of reflection: the angle of incidence is equal to the angle of reflection and incident rays, reflected rays and normal rays drawn at the point of incidence to the reflecting surface lies in the same plane.

1. Incident ray: The ray of light which strikes any surface is called the incident ray.
2. Reflected ray: The ray which comes back from the surface after reflection is called reflected ray.

1. Angle of incidence: Angle of incidence is a measure of deviation of something from "straight on". Angle of incidence is always equal to angle of reflection.
2. Angle of reflection: The angle between normal and reflected rays is called angle of reflection.

1. Angle of incidence: Angle of incidence is a measure of deviation of something from "straight on". Angle of incidence is always equal to angle of reflection.
2. Angle of reflection: The angle between normal and reflected rays is called angle of reflection.

Image formed by plane mirror is virtual, upright and of the same shape and size as of the object.

Lateral inversion is the reversal experienced by the image formed in a flat mirror. Although the image is the correct way up, its left and right sides are transposed.

When a beam pass of parallel light rays is incident on a smooth and plane surface, the reflected rays will also be parallel. This type of reflection is called Regular Reflection.

When a beam of parallel light rays is scattered in all directions. Thus, the parallel rays incident on the surface will reflect in different directions. This type of reflection is called "Irregular or Diffuse Reflection".

Sit in front of a mirror, tell your friend to hold a mirror behind you to see your hair cut, your hair image will be shown in the mirror in front of you, this is the best example of reflected light can be reflected again.

Seven colours of rainbow:

The eye has roughly spherical surface. The outer coat of eyes is white and tough to protect the interior of eyes from any kind of accident. Its transparent front part is called cornea, behind the cornea there is a dark muscular structure called iris. In the iris there is small opening called pupil. The size of the pupil is controlled by the iris, the iris control the amount of light entering into the eye.

The lens focuses light on the retina which contains several nerve cells. Sensations felt by the nerve cells are then transmitted to brain through the optic nerve.

At the junction of the optic nerve and the retina, there are no sensory cells, so there is no possibility of vision at that spot, thus it is called blind spot.

Eyelids prevent any object from entering the eye, eyelids also shut out light when not required.

Myopia is a vision condition in which close objects are seen clearly, but objects farther away appear blurred. Most commonly myopia can be corrected through the use of corrective lenses, such as glasses or contact lenses. It may also be corrected by refractive surgery, though there are cases of associated side effects. The corrective lenses have a negative optical power (i.e. are concave) .

Hypermetropia means long sight and is where the image of a nearby object is formed behind the retina. This could be because the eye is too short, or the cornea or crystalline lens does not refract the light enough. A hypermetropic person may have blurred vision when looking at objects close to them, and clearer vision when looking at objects in the distance. By placing a convex (plus powered) lens in front of a hypermetropic eye, the image is moved forward and focuses correctly on the retina.

In old age eyes eye lens becomes cloudy, and person develops a cataract that is loss of vision. This defect can be treated by replacing opaque lens with a new artificial lens.

In old age eyes eye lens becomes cloudy, and person develops a cataract that is loss of vision. This defect can be treated by replacing opaque lens with a new artificial lens.

• If advised use suitable spectacles
• avoid too much or too little eyes
• do not look at the sun or a powerful light directly
• never rub your eyes
• wash your eyes properly and frequently with water
• Always read at the normal distance for vision.

Braille is a writing system which enables blind and partially sighted people to read and write through touch. It was invented by Louis Braille.

The owl has a large cornea and a large pupil to allow more light into the eye. It has large number of rods on its retina and few cones that enables it to see properly in dim light or in dark.

In diffused reflection each ray obeys the law of reflection, thus there is no failure of law of reflection.

1. regular reflection because mirror has smooth surface
2. diffused reflection because cardboard has irregular surface.
3. diffused reflection, because a piece of paper appears smooth but it has lot of minor irregularities.

Normal eye can clearly see distant objects as well as object nearby.