APPLICATION OF LIGHT WAVES

 

APPLICATION OF LIGHT WAVES

1. Simple lens camera

This camera consists of a light-proof box with a converging lens in front and a light sensitive film at the back. The function of the lens is to focus images of the object to be photographed onto a light-sensitive plate or film. The bellows or focusing rings is used to adjust the distance between the lens and the film. The diaphragm ( it regulates the size of an aperture or opening which controls the amount of light energy sensitizing the film) and the shutter( it controls the time intervalduring which light is allowed to fall on the film) control the amount of light entering the camera.

2.  Film projector

The Projector is an instrument for projecting on a screen an enlarged image of a transparent object e.e a slide

Projector Parts and their functions

I.                     Light source- to illuminate the object which is usually non-luminous

II.                    The condenser: it consists of two plano-convex lenses. It collects the light from the light source and concentrate it on the slide or transparency and illuminates every part of it strongly and evenly.

III.                  The slide carrier- is a framework in which the slide is place upside down, so that it will appear erect on the screen.

IV.                  The Projection lens- it produces a real enlarged and inverted image of the slide and focus it on the screen.

V.                   The screen- it receives the image

3. The human eye,

The eye has a refracting system containing a converging lens which forms an image of an object in front of the eye on a light sensitive layer at the back of the eye.

 Some part of human eye and their functions.

I.                     The Cornea- the thick transparent bulge in the front part of eye. It serves as a protective covering in front of the lens and allows light into the eye.

II.                    The Aqueous humour- is the transparent liquid between the cornea and the lens and the vitreous humour is a jelly-like liquid between the lens and the rest of the eyeball.

III.                  The Iris is behind the cornea- is the part which gives the colour of the eye. It acts as a stop or diaphragm of variable size. It has a tiny opening at its centre called the pupil which regulates the quantities of light entering the eye. The pupil looks black because of the inner layer of the eye, the choroid, is black.

IV.                  The Crystalline lens which focuses the light from the object on to the light sensitive retina.

V.                   The Ciliary muscles which support the lens and attach it to the wall of the eye. It alter the focal length of the lens changing its shape.

VI.                  The Retina is the light sensitive area of cells at the back of the eye.

VII.                The Yellow spot is the most sensitive spot of the retina. It is here that light entering the eye are usually brought to a focus and here the clearest image is formed.

VIII.               The Blind spot is the point of exit of the optic nerve from the retina. It is insensitive to light.

IX.                  The Sclerotic layer is the outer covering of the eye.

The optical system of the eye consists of the cornea, the lens, and the aqueous and the vitreous humour. They operate to form  a real and inverted image of an external object on the retina. The retina transmits the impression created on it by this image to the brain through the optic nerve. The brain then interpretes the impressions.

Accommodation is the ability of the eye to alter or adjust the focal length of its lens so as to form clear images of objects at different distances on its retina. The adjustment is brought about through the action of the ciliary muscles.

Binocular vision is the overlapping of the two images formed by both eyes which gives an impression of depth and solidity and makes it possible for us to see things in relief. Such a proper perspective of an object is impossible with one eye.

Persistence of vision is the retention of the vision of the image.

EYE DEFECT AND CORRECTION

I.   Myopia (short sight): A short sighted person cannot see distant objects clearly. This is because his eyeballs are too long or crystalline lens is too converging that rays from distant objects are brought to a focus in front of the retina instead of at the retina. This can be corrected by placing  a suitable concave or diverging lens in front of the eye.

2. Hypermeiopia (long sight): A long sighted person can see far object but cannot see near objects clearly. This is caused by the eyeball being too short or the crystalline lens not being sufficiently convergent. The defect is corrected with the aid of a suitable converging lens placed in front of the eye.

3.  Presbyopia: is an age-related condition that causes blurred near vision. This is caused by  changes to the lens inside the eye, the lens become harder and less elastic, making it difficult for the eyes to focus on close object. The defect is corrected with the use of bifocal eyeglasses.

4. Astigmatism is a condition in which eyeball isn’t completely round. people can get it after an eye injury, an eye disease or surgery. It causes blurred distance and near vision.

5. Colour blindness: a reduced ability to distinguish between certain colour.

Difference between the eye and the camera lens.

Human Eye	Camera
1. A biological organ	Mechanical device
2. Variable focal length	Constant focal length
3. Distance between the lens and the retina is fixed	Distance between lens and film can be varied
4. suffer from defects of vision	Do not suffer defect of vision

 

Similarities between the eye the camera.

I.                     The camera includes light-tight box painted black inside. The human eye is impregnated with black pigments within.

II.                    The pupil in the eye serves the same purpose as the aperture of the camera.

III.                  Both the eye and the camera have converging lens to focus rays from an external object.

IV.                  Both have light sensitive material on which the rays are focused, the retina in the eye and the film in the camera.

V.                   The iris is the serves the same function as the diaphragm in the camera, to regulate the amount of light entering the equipment.

TYPES OF MICROSCOPE

classification of microscope: simple microscope compound microscope , telescope astronomical telescope, Galilean telescope, terrestrial telescope, prism binocular

The Simple Microscope has a single converging lens of short focal length.

The Compound Microscope consist of two converging lenses of short focal length. The eyepiece has a longer focal length than the objective.

The Astronomical Telescope consists of a converging objective lens of long focal length and a converging eyepiece of short focal length. At normal adjustment the image is formed at infinity.

The Prism Binocular are in reality a pair of twin telescope mounted side by side, one for each of the two eyes. Each binocular consists of two converging lenses and a pair of reflecting prisms which invert the rays to give erect images.