Lighting System of a Car | Car Lightings

Lighting system

The lighting system in an automobile includes the following: head lights, direction signal lights, stop lights, back up lights, tail lights, blinker lights, side maker lights and the interior lights.


Head lights illuminate the highway sufficient to permit safe night driving. These are usually provided two or more beams. One beam provides maximum illumination for driving. The other beam is so designed to permit its deflection to the ground and to the side of the road. This beam becomes essential to minimize glare when passing other vehicles on the road. The head light has two filaments for the above purpose, an upper beam and a lower beam. When the light switch is pulled out, the circuit from the battery to the head lights is completed. This circuit is through the foot selector switch. This switch has to positions, low beam and high beam. These are also called passing beam and high beam.


Tail lights are used to illuminate the rear of the vehicle, including the licence plate, so that both vehicle and licence plate can be seen by the drivers of other vehicle. Tall lights usually incorporate stop lights, which flash red signal whenever the brakes are applied.

In addition to the head lights, low intensity parking lights are usually provided in the front of the vehicle, either as separate units or as part of the head lamps.

Blinker lights are installed in many cars to provide a means of signaling when a car is stalled on the highway or has pulled off to the side. The blinking is much more noticeable than a steady light and provides a warning to the approaching vehicles.


Back up lights are installed in many vehicles to provide means of signaling when reversing. These lights come on when the driver shifts into reverse gear. This closes a switch linked to the selector lever which connects the backup lights to the battery.

Flashing signals or turn sign lights on each side of the vehicle on the front and rear indicate to other vehicle drivers and road users, the direction in which the vehicle is about to turn. In operation, the lights are caused to flash about 80 times per minute.

The turn signal lights are so wired to operate in a flashing mode when the front and rear lights on the right and left sides are activated by the turn signal light switch assembly shown .Flashing of the twin signal bulbs is controlled by the turn signal flasher shown in the picture A bimetallic strip in the flasher causes the circuit to open and close. As the current flows through the bimetallic strip it heats up and expands and thereby opens the circuit. As the strip cools, it contract and closes the circuit again.

Interior lights provided in a vehicle include instrument panel lights, various warning indicator and courtesy lights which turn on when a car door is opened.


The lighting system also includes lights inside the body illuminate the compartments in which the passengers ride, special lights to illuminate the key hole for the ignition key or the inside of the glove compartment. Map lights, trunk compartment lights, radio dial lights, cloak lights, and engine bonnet lights are also provided in some vehicles.

In addition, one or more special lights, designed as signals to the driver are incorporated. Such special lights include a red signal light to indicate when the high beams of the head lamps are on, when it is possible to go into overdrive, to indicate that the lubricating oil pressure is low, that the cooling water temperature is too high or too low, or that the generator is not charging.

Holography | Hologram 3D Images


A photograph is a two-dimensional record of light intensity received from a three-dimensional object.

Holography is a technique for recording optical images. It was developed by Gabor in the year 1947.The term holo means whole or complete and graphy means recording. Holography literally means complete recording.

01 - holography - hologram image

Holography records both amplitude and phase of light waves to produce a three-dimensional effect.

Basic principle

In holography, the image of an object is not directly recorded but the light waves reflected from the object after interference with direct ray are recorded. The photographic record is called hologram.

When the hologram is illuminated by coherent source of light, a three-dimensional image of the original object is formed.

01 - holography - VIEWING A HOLOGRAM

It should be noted that a hologram has no resemblance to the original object but it contains all informations about the object in the form of optical code.

Holography is based on the principle of interference and hence the light waves with high degree of coherence are required for its realisation. Hence, laser beam is used for preparing hologram.

Steps in holography

Holography is a two-step process.

Step-1 Transformation of the object into hologram i.e., an object illuminated by coherent light is made to produce interference fringes in a photographic plate.

Step-2 Re-transformation or reconstruction of hologram into an image of the object i.e., reillumination of the developed interference pattern by light of same wavelength to produce a three-dimensional image of the original object.

Construction or recording of a hologram

The process of making a hologram is called recording or construction of hologram.

The arrangement for recording a hologram is shown in the picture

A beam from helium-neon laser is divided into two beams. By means of a beam splitter. The transmitted beam  called object beam illuminates the object whose hologram is to be recorded. A part of this light scatters from the object and falls on a photographic plate P.

The reflected beam a from the beam splitter called reference beam, also falls on the photographic plate. These two beams interfere with each other and they produce interference pattern which is recorded on the plate.

The pattern is very fine with the spacing between fringes is as small as 0.001 mm. When the plate is developed, a hologram is obtained which appears transparent.

01 - holography - hologram construction

Reconstruction of a holographic image

The method of displaying a hologram is known as reconstruction. The object is recreated from the hologram by directing a beam of light to the holographic plate.

The laser beam from a laser source is reflected from a mirror. Now, the laser beam known as readout beam, interacts with the interference pattern on the plate. It produces two images from diffracted beams emerging from the hologram.

One of them appears at the original position occupied by the object called virtual image and the other, the real image can be photographed directly without using a lens.

The virtual image which can be seen by looking through the hologram, appears in complete three-dimensional form.

If our eye is moved from the viewing position, the perspective of the picture changes and it is possible to see the other side of the object.