OPTICS

What is light? Light is a form of energy that can be detected by the human eye.

What is natural light source? The Sun is a natural light source, the most abundant and least expensive light source in the world

What is a radiant? A radiant is energy that is sent out in the form of waves or rays.

What is radiation? Radiation is the heat transfer of radiant energy waves or rays such as light. wavelength (color, frequency) corresponds to the energy of the light

What is radiant energy? Radiant energy is energy transferred or emitted as waves or rays in all directions.

What is an artificial light source? An artificial light source is a human made source of light.

What is illumination? The amount of light cast on a subject.

What is the main source of illumination on Earth? The Sun is the main source of illumination on Earth.

What is artificial illumination? Artificial illumination is light energy that is man made so humans could see in the dark.

Where does light energy come from? Light energy comes form two different sources, natural and artificial.

What is the most important source for natural light? The sun is the most important source for natural light.

What are luminous objects? Luminous objects are objects that give off their own light.

What are nonluminous objects? Nonluminous objects are objects that do not give off light.

Why is the Moon nonluminous? The Moon is nonluminous because it reflects light from the Sun

What are some common forms of luminous energy? Some common forms of energy are: Chemical energy Electrical energy Nuclear energy Thermal energy

What does incandescence mean? Incandescence means the release of visible light by a hot object.

What does phosphorescence mean? Phosphorescence is the process of giving off light for sometime after receiving light from another source.

What is fluorescence? The release of light from a substance caused by exposure to radiation from an external source www6. .lasso

Where are fluorescent lights used? Fluorescent lights are used in: Schools Offices Homes

What is Chemiluminescence ? Chemiluminescene is the process of changing chemical energy into light energy with little or no change in temperature. A chemical reaction that gives off energy in the form of light instead of heat. We all love glow sticks, which illustrates this process perfectly. When a glow stick is bent, a glass vile inside releases the chemicals and produce light.

What is Bioluminescence? Bioluminescence is any process used by living things to transform chemical energy into light energy.

Give examples of bioluminescence. Firefly Glow worm Zebra Fish Hawaiian bobtail squid

Bacteria Fungi (mushrooms)

Daytime Nighttime

Which of the following are luminous? A. Campfire B. The Moon C. A hot toaster filament

WHY? The campfire and hot toaster are luminous. For, luminous objects are objects that give off their own light.

Explain in your own words the difference between a phosphorescent source and a fluorescent source. The main difference is that a fluorescent source emits light only while it is receiving energy from elsewhere, but a phosphorescent source can continue to emit light for some time after the source of energy is removed.

Describe how it can also be nonluminous. The flashlight can be nonluminous when it is turned off.

What is a dark and light shadow? A shadow is formed where light is 'missing'. A dark shadow (umbra) is formed where no light falls and a light shadow (penumbra) is formed where some light falls, but some is blocked. If the light source is very tiny and concentrated in one place (a point source) only a sharp shadow is formed.

If the source is broader light from the top of the source causes a lower shadow than that from the top. You therefore get partial shadow or penumbra as well as umbra.

If we use coloured lights at different points we can see the effect of these multiple shadows:

The size of a shadow changes as you move the source closer or further from the screen

As you move the object closer or further from the screen.

What is reflection? Reflection occurs when a ray of light is returned after hitting a surface.

What is an incident ray? An incident ray is a light ray that strikes a surface. When light strikes a reflecting surface, it bounces off the surface.

What is a reflected ray? A reflected ray is the light that is reflected from a surface.

To find out in which direction each ray of light is traveling, you can measure an angle. To do this, draw a reference line that is perpendicular (90 degrees) to the reflecting surface at the point where the incident ray strikes the surface. This line is called normal (definition-reference line that is perpendicular - 90 degrees- to the reflecting surface). The angle between the incident ray and the normal is called the angle of incidence, i. The angle between the normal and the reflected ray is called angle of reflection, r.

Two laws of reflection? 1. The angle of reflection, r, is always equal to the angle of incidence, i. 2. The incident ray, the normal, and the reflected ray are always in the same plane.

What happens to light when it reflects off a rough surface? When light reflects off a rough surface the light reflects in all directions, so very little light will defect.

What is transparency? Transparency is a measure of how much light can pass through a material.

A shadow results because light travels in straight lines from its source and does not bend around objects

How are materials classified? Materials(matter) are classified as transparent, translucent and opaque.

Describe transparent and give an example. Transparent: The ability to see through an item. Allowing light to pass through so that objects may be clearly seen. The opposite of transparent is opaque. Example: Plastic wrap

Describe translucent and give an example. Translucent: Allowing some light to pass through an object without seeing clearly through the object. Example: skin, frosted glass and clouds

Flesh is transparent to X-rays, while bone is not, allowing the use of medical X-ray machines.

Describe opaque and give an example. Substances that allow no light through them. Opaque means not see-through. Not allowing light to pass through, it is the opposite of transparent. Examples: milk, wood, stone and brick

Light will travel in straight lines until it strikes something.

When does reflection occur? Reflection occurs when a ray of light is returned after hitting a surface.

Are the following transparent, translucent or opaque? A. Very Smoky Air B. Waxed paper C. A copper plate D. An ice cube

What happens when a beam of light strikes a rough or irregular surface? The angle which light strikes and reflects will be equal at each point of the angle, but the surface has many different directions and therefore so will the reflected rays. As a result, a rough surface will be visible from almost any position. In contrast, to see light from a mirror, the eye must be looking in the direction in which the angle beam is reflected.

What is reflected light? It is the concept that all objects reflect light: some more than others. It is this reflected light that enters the eye and enables us to see the object such as surface texture, colour dimensions.

What is regular reflection? The reflection of light off a smooth, shiny surface.

Law’s of Reflection There are three laws of reflection that describe the reflection from plane mirrors: The angle between the incident ray and the normal is equal to the angle between the reflected ray and the normal. 2. The incident ray, the normal, and the reflected ray are all in the same plane. 3. Incident ray and reflected ray are on different sides of the normal

The angle between the incident ray and the normal is equal to the angle between the reflected ray and the normal.

2. The incident ray, the normal, and the reflected ray 2. The incident ray, the normal, and the reflected ray are all in the same plane.

Incident ray and reflected ray are on different sides of the normal

You can improve your pool game by applying the laws of reflection.

What is diffuse reflection? When light hits an irregular surface reflected light scatters in many directions.

Why is diffuse light easier on your eyes than other types of reflected light? Diffuse light is easier on your eyes because it’s light is reflected and scattered in many directions. Direct light and glare strain your eyes. Diffusion allows you to see object with ease. Diffusion is found in homes, schools and places of work.

Describe regular reflection and diffuse reflection. Regular reflection is the reflection of light off a smooth, shiny, regular surface. In diffuse reflection, light is reflected off an irregular surface in many directions.

What are plane mirrors? Plane mirrors are regular flat mirrors.

What is refraction? The action of changing the direction of a light wave, so the light enters the object in one direction, and leaves it in another. Looks like a broken pencil

What happens to the light ray when it passes through air and glass? If a light ray passes form a less dense substance such as air into a denser substance such as glass, it will bend towards the normal.

What happens when a light passes from a denser to a less dense material? When light passes form a denser to a less dense material, it will bend away from the normal. The amount of refraction depends on the angle of the incoming ray

What happens when a light wave impacts another material at right angles to its surface? Light waves that impact another material at right angles to its surface do not bend because each point on the wave front reaches the boundary at the same time. The light ray is approaching the boundary traveling along the normal. If the block has parallel sides (as in my sketch) the ray comes out of the block at the same angle as it entered,

Why do birds diving do fish usually enter the water at right angles? Birds dive at right angles perpendicular to the water’s surface so their vision is not distorted.

You can see why birds dive at right angles You can see why birds dive at right angles. If not their vision get distorted and they are not successful at catching their food.

This is how the archer fish positions itself for food This is how the archer fish positions itself for food. The key to food is to travel along the normal.