light and sight

Chapter 2

Our Eyes are probably the most important of our five senses.

Our Eyes enable us to see and interpret the shape, colors, and dimensions of objects in the world.

The Eyes is able to see in dim or bright light but it cannot see objects when light is absent. It changes light ray into electrical signals then sends them to the brain where this are interpreted as visual images.

The Structure of Human Eye

Cornea – forms the eyeball’s coating. Its serves as the window of the eye.

Lens – it is a jelly-like assembly of tiny transparent fiber. It bends light rays that enters the eye.

Iris – it is made of two different muscle fibers. it controls the size of the pupil.

Pupil – allows to pass into the eyes aqueous humour to the lens.

Ciliary Muscle – it contacts and expands to control the curvature of the lens.

Vitreous humor – is a cavity filled with fluid. It provide nourishment to the front of the eyes and maintain the eye pressure.

Retina – serves as screen where the image is form. It contains millions of tiny nerve cells called Rods and Cones. Rod vision on dim condition and Cones is vision for bright condition.

Fovea Centralis – is where the eyes shapestvision and location of the most colorperception.

Optic nerve – is the pathway that the light rays take from the retina to the processing center of the brain.

In chapter 4: how the eye produces an image.

- it is a form of energy. It can be converted into other forms.

Light to Chemical Energy(Photosynthesis) and (Photographic film)

Other form of energy can be converted into light.

Electrical energy Light(light in Bulb, fluorescent, tv)

Chemical energy Light(Candle fame, flame in lamp)

Sun is the main source of energy on the earth. it warms the earth and sustain life in it.

It emits light.. This kind of object just like electric bulb, flash light, burning candle are called luminous bodies.

Most object around us are nonluminousbodies, these do not emits light but are illuminated by light. Those objects which allows light to pass through are called Transparent materials; while those object which do not allow the passage of light are called Opaque.

We see objects by light the emits, reflect or transmit.

Ray – is a beam of light. It is usually represented by a straight line with an arrow head pointing to the direction of travel. Lighttravels in

straight line in one medium.

Opaque materials can be smooth or rough.

When reflection of light travel in only one direction it is called Regular reflection.

When reflection of light travels in all direction it is called Diffuse reflection.

Questions:

1. How does the pencil appears? Describe it.

2. What could be the explanation of your observation?

When light passes from one transparent medium to another at an angle other than 90 with the boundary, the light bends this is called Refraction.

Reason:

Refraction happens due to the change in speed of light as it passes from one medium to another.

Observe the video.

Olaf Roemer a Danish astronomer the first who made rough estimate of speed of light in 1676.

A.H.C. Fizeau measure speed of light using apparatus.

Foucault a French physicist improve Fizeau’smethod of measuring speed of light by substituting a rotating mirror for the toothed wheel.

A.A. Michelson an American physicist, using the same method as Foucault’s, he calculated value of 2.997025 x108 m/s

accepted value 3.0 x 108 m/s.

When light separates into different colors this called Visible Spectrum, as it passes through a prism.

The Spectrum consist of colors of the rainbow: what are those?

Red = Orange = Yellow = Green = Blue = Indigo = Violet =

What do you think the most prominent colorsamong the 7 colors of light?

Answer:

Red, Green and Blue (RGB). these are the primary colors of light.

The different combination of these color RGB forms other color.

Red + green light =

Green +Blue light =

Red + blue light =

Red + Green + Blue = White

Paint

Yellow + Red =

Yellow + Blue ` =

Yellow

Cyan

Magenta or Purple

Orange

Green

Group work: write the result of the object when illuminated by the indicating color light. Use the graphs in figure2.8 for referral at page 28 in Physics book.

Blue Sky

Atmosphere is made up mostly by Nitrogen and Oxygen molecules.

Violet is scattered the most by the molecules. The next are blue, green, yellow, orange and red.

Though the violet is scattered more than blue, are eyes are not very sensitive to violet. The scattered blue lights predominates.

The color of the sky varies with the condition of the atmosphere.

The Red Sunset

Retina has special cells called Rod and Cones. Cones are sensitive to color and enable us to

distinguish colors.

Chemicals in cones are sensitive to red, green and blue light (RGB).

The color of objects are the result of interaction of light with materials.

The scattering of the colors by small particles in the atmosphere gives us nature’s palette of amazing colors that we see everyday.