FP_LESSON 7

Prepared by: CAM Gonzales

TWO (2) TYPES OF LIGHT

Lights can largely be classified into visible and invisible light.

1. Visible Light (wavelength: 400-700nm) Is the type of light that produces different sensations when reaching the human eye. It is the type of light, which is capable of exciting the retina of the human eye.

2. Invisible Light (lights with a shorter or longer wavelength) lights in which their wavelength are either too short or too long to excite the retina of the human eye Example: X-ray, Ultra-violet, and Infra-red lights.

WHITE LIGHT

WHAT IS WHITE LIGHT?

White light that is composed of a wide range of electromagnetic frequencies and that appears colorless to the eye. White light is actually made of all of the colours of the rainbow because it contains all wavelengths, and it is described as polychromatic light. Light from a torch or the Sun is a good example of this.
When all the wavelengths between 400 to 700 nn are presented to the eye in nearly equal quantity, we get the sensation or perception of colorless or white light. If a narrow beam of white light can pass 25 through a prism it will bend the light of shorter wavelength more than those with longer wavelength thus spreading them out into visible spectrum. These are the color of the rainbow.
Rainbow colors include: Red, Orange, Yellow, Green, Blue, Indigo, Violet
If we divide the wavelength of visible light into nearly equal quantity, we will produce blue, green, and red colors.

ELECTROMAGNETIC SPECTRUM

The electromagnetic spectrum is the complete range of electromagnetic radiation arranged by frequency or wavelength, including radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. Visible light is only a small part of this spectrum. Waves with lower frequencies than visible light—such as infrared, microwaves, and radio waves—have lower energy and are generally not harmful. In contrast, waves with higher frequencies—ultraviolet, X-rays, and gamma rays—have higher energy and can be harmful to living organisms, with gamma rays being the most damaging, though Earth’s atmosphere helps protect us by absorbing most of them.

WAVELENGTH vs. FREQUENCY

The distance from crest (highest point) to the wave of the next succeeding crest is called Wavelength meanwhile, the number of waves passing in a given point in one second is called Frequency.

PHOTOGRAPHIC RAYS

X-ray- Light with the wavelength between 01 to 30 millimicrons or nanometer. It is produced by passing an electric current through a special type of vacuum tube. It was incidentally discovered by Conrad Wilhelm Roentgen. This type of light works in the principle of shadow photography.
Ultra-violet ray-(Before the violet) Radiation having a wavelength of 30 to 400 nanometers designed to photograph fingerprints in the multicolored background, documents that are altered, decipherment of erasing writing, and developing invisible writing. It is commercially known as “Black Light”.
Visible Light-It refers to the type of radiation having a wavelength of 400 to 700 millimicrons designed for ordinary photographing purposes.
Infra-red- (Beyond the Red) Considered as the photographic rays with the longest wavelength ranging from 700 to 1000 millimicrons. It is designed to take photographs of over-written documents, obliterated writing, and charred documents or for blackout photography. It is sometimes referred to as heat rays.

THEORIES OF LIGHT

CORPUSCULAR THEORY

Sir Isaac Newton, in the late 17th century, proposed the Corpuscular Theory of Light. He suggested that light consists of tiny particles called corpuscles, which travel in straight lines and are emitted by light sources. This model explained reflection and refraction, but it could not account for phenomena like diffraction and interference.

WAVE THEORY

This theory, developed by Christiaan Huygens, describes light as a wave that propagates through a medium called the ether, explaining phenomena like reflection, refraction, diffraction, and interference.

MODIFIED WAVE THEORY

It refers to how Heinrich Hertz experimentally validated and expanded upon James Clerk Maxwell's theory of electromagnetic waves, proving the existence of radio waves which Maxwell had predicted mathematically, essentially confirming that light is a form of electromagnetic radiation with a specific wavelength range .

BEHAVIORS OR PROPERTIES OF LIGHT

REFLECTION

It is the deflection or bouncing back of light when it hits a surface

REFRACTION

The bending of light when passing from one medium to another

DIFFRACTION

The bending of light when it hits a sharp edge opaque object

TRANSMISSION

The transmission of light occurs when light hits an object that is transparent or translucent and light can penetrate the material to travel all the way through.

ABSORPTION

Absorption of light is when light does not pass through a material.

SCATTERING

Light scattering is when light rays change direction after hitting an obstacle, such as dust, water vapor, or gas molecules

KINDS OF OBJECTS

TRANSPARENT

Transparent objects allow light to pass through them without being scattered or absorbed. This means that you can see through the object.

TRANSLUCENT

A translucent object is an object that allows some light to pass through it, but not all. When looking through a translucent object, the image appears blurry.

OPAQUE

Opaque objects are objects that do not allow light to pass through them.

COLORS OF LIGHT

The primary colors of light are red, green and blue. Mixing these colors in different proportions can make all the colors of the light we see. This is how TV and computer screens work. If you look at a screen with a magnifying glass you will be able to see that only these three colors are being used. For example, red and green lights are used to make our brain perceive the image as yellow. When colored lights are mixed together, it is called additive mixing. Red, green and blue are the primary colors for additive mixing. If all of these colors of light are shone onto a screen at the same time, you will see white.

SUMMARY OF KEY CONCEPTS

Frequency is the number of complete waves per unit of time.
Wavelength is the distance between two peaks
Red has the longest wavelength.
The absence of color is called black.
The presence of all color is called white.
Light is important in photography.
Light is radiant energy that makes things visible.
The speed of light is 186,000 miles per second.
Light may be visible or invisible.
Red, green and blue are the primary colors of light.

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