readings...

The easiest way to understand lenses is to know its application. Mostly the application is on optical instruments.

The 1st one I posted was erratic..Pls. consider the link for further reading.

Enjoy and have fun!!!

http://www.mysciencesite.com/optics4.html

Lens, light and your eyes...

 http://www.mysciencesite.com/optics4.html
(Pls follow this link)

How does a mirror reflect light?  The mirrors that you use everyday, the ones you have in your homes, have flat surfaces. Because of this, they reflect almost all of the light. The image you see, the virtual image, the one in the mirror is the same size as the real object.  The virtual image appears to be behind the mirror. The distance between the mirror and the object is the same as the distance between the virtual image and the mirror. The real object and the virtual image are basically identical except for one thing - the virtual image is reversed.

If you have ever noticed the mirrors that hang in stores, you would have realized that not all mirrors have flat surfaces. There are curved mirrors. These mirrors also refect light, but because they are curved the virtual image will look different. Curved mirrors produce the effect of enlarging or reducing. There are two types of curved mirrors: concave and convex.  A spoon is a good example of a refecting surface with one side being convex  the other concave. Concave increases the size of the object while convex decreases the size.

(

convex mirror

)

concave mirror

light

light

What exactly are lenses?  A lens is a transparent material, such a glass, that has either one curved surface and one flat surface or two curved surfaces. As with mirrors, these two lenses are either convex or concave. Convex lenses are thicker in the middle then the edges and concave are thicker at the edges then the middle. When light travels through lenses, refraction occurs. The light bends either outward or inward, it depends on the lens.

The lens of your eye is a double convex lens. Its job is to focus the image on the retina of the eye. If one is farsighted, the lens in the eye causes the focus to be behind the retina. These people see far but have some difficultly seeing close-up. The lens focuses behind the retina because the actual eyeball is too short from front to back. To correct this farsightedness, the person would wear glasses or contacts with convex lenses. What would be the result and treatment if a person's eyeball was too long from front to back? (answer is at the bottom)

NEAR SIGHTED  Corrective

Lense

Your eye and a camera are quite similar. Both use convex lenses to focus the image upside-down. Your eye uses its retina to detect the image whereas the camera uses film to detect the image.

If one is nearsighted, the lens in the eye causes the focus to be behind the retina. These people see close-up but have some difficultly seeing far away. The lens focuses infront of the retina because the actual eyeball is too long from front to back. To correct this nearsightedness, the person would wear glasses or contacts with concave lenses. Take a look at the two diagrams.

Answer

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reminders: 2nd quarter project

Pls. be reminded of your 2nd quarter project. You are going to select one model of the improvised sonometer from the 1st quarter project proposals. Then you will make it and pass it one week after your quarter exam. This is a class project.

Announcement

Long Exam on Monday for Camia and Jasmine. Tuesday for Sampaguita.

Coverage:
1. Nature of light - please include the reading assignment about the different scientist who measured the speed of light
2. Electromagnetic Spectrum - its components and applications
3. Colors and Pigments

please Schedule your consultation this week before the exam if you think you really need a follow-up on the above topics.

Good luck for your 1st long exam.

exercise: colors and pigments

Physics 1

Exercise #2

1. Two lights are arranged above a white sheet of paper. When the lights are turned on they illuminate the entire sheet of paper (as seen in the diagram below). Each light bulb emits a primary color of light - red (R), green (G), and blue (B). Depending on which primary color of light is used, the paper will appear a different color. Express your understanding of color addition by determining the color that the sheet of paper will appear in the diagrams below.

2. If magenta light and yellow light are added together, will white light be produced? Explain.

3. Blue jeans appear blue because the jeans are permeated by a chemical dye. Explain the role of the dye. That is, what does the dye do (absorb or reflect) to the various frequencies of white light?

4. A red shirt looks red when visible light ("ROYGBIV") shines upon it. Use your physics understanding to explain this phenomenon.

5. In the diagrams below, several sheets of paper are illuminated by different primary colors of light (R for red, B for blue, and G for green). Indicate what primary colors of light will be reflected and the appearance of the sheet of paper. (Note the similarity between this problem and the above problem.)

Nature of Light

History and Properties of Light:

·         Sir Isaac Newton:

§  separates white light to different colors

§  Corpuscular Theory of Light – light as particles

§  Newton’s rings which is a disparity of his particle theory

·         Christian Huygens:

§  Supporter of wave theory

§  Wave fronts are made up of tinier wave fronts

·         Thomas Young:

§  Proponent of wave theory of light

§  Proved that light is a wave by his double slit experiment

·         Albert Einstein:

§  Photoelectric effect

§  Light is made up of photons whose energy is dependent on the frequency

§  Energy is quantized

·         James Clark Maxwell:

§  Light is a vibration of electric and magnetic field which are perpendicular to each other

§  Light is a form of electromagnetic wave with a speed of 3 x 10⁸ m/s

·         Quantum Theory of Light:

§  Light has a dual property but will not occur simultaneously.

§  Light behaves as particle when interacting with matter but will behave as a wave during its travel.

o   Electromagnetic  Spectrum:

As you can see in the figure, we have a decreasing trend in wavelength from radio to gamma ray. Since wavelength is inversely proportional to frequency, it’s the opposite trend in terms of frequency. Visible light is only a small part of EM spectrum which composes seven colors from red to violet.

-all the components will exhibit reflection, refraction, diffraction and interference

- will travel without a medium at a speed of 3 x 10⁸ m/s

- will obey the wave equation v = wavelength x frequency

COLORS & PIGMENTS

Primary Colors of Light: will produce white light when combined

1.       Red

2.       Green

3.       Blue

Light addition is the concept behind colored TV screen. When two of the primary colors are combined, it will produce another color. The set of different colors produced are the secondary colors of light.

COLOR ADDITION

-          Combining colors of light will produce another different color.

Red + Green = Yellow

Green + Blue = Cyan

Red + Blue = Magenta

Complimentary Colors of Light

-          Any two colors of light that when mixed together in equal intensities produce white.

Ex: red and cyan; applying color addition:

Red + Cyan = Red + (Green + Blue) = Red + Green + Blue = White

-          One primary color and 1 secondary color

-          Opposite position on the color wheel

Primary Colors of Pigments: when combined together, it becomes black

1.       Cyan

2.       Magenta

3.       Yellow

When any of the two pigments are combined, it produces different color. The colors produced are the secondary colors of pigment.

1.       Cyan + Magenta = Purple

2.       Magenta + Yellow = Orange

3.       Yellow + Cyan = Green

-          Pigments absorb some of the incident light and reflecting some of it to produces color of the object. It follows color subtraction.

Ex: Yellow pigment: yellow as the secondary color of light is produced by combining red and green, so it absorbs blue. Using color subtraction:

White – Yellow = Red+ Green + Blue – Blue = Red + Green = Yellow.

-          Meaning, it becomes yellow because the light used is white light. It absorbs the blue and reflected the red and green light which makes it yellow. But in the case that the light used is green, the pigment now will become green because of the only color present. Since, yellow pigment cannot absorb green, it is being reflected. In short, the color of an object depends on the source of light used and the type of primary color/s it reflected.

Reading Assignment:

Read on the application of the following:

1.       Scattering Effect

2.       Selective Transmission

3.       Selective Reflection

Take home exam

Instructions:
1. Copy the given problem set in a one whole sheet of paper with your complete solutions. Be sure to enclose your answers in a box , and to include the units . To receive full credit, you must show all your work on this test paper.
2. This exam is due on Monday, August 17, 2011 @ 8:00 am. Please consider the time...Late submission will have a corresponding deductions.
3. The total score for papers with almost the same answers will be divided among themselves. Get rid of copying one's ideas. No sharing of ready made answers by this time...Don't forget that copying is one form of cheating which is a major offense (:

Begin here:

Physics 1

Properties of Sound

Take Home Exam

Name: __________________________________- Year & Section: __________________

1.  A deep sea ocean vessel uses SONAR to detect the ocean's bottom. Sound waves are emitted from the surface of the ocean and travel through the water at 1450 m/s. The ocean bottom is 1630 m below the surface. Determine the amount of time that passes before the sound waves are reflected back to the surface.
2. What happens when a sound wave hits a concave shaped surface? 
3. Discuss the process of the following using sound wave concept: Please select only one application
a. SONAR
b. ultrasound
c. ultrasonic flaw detector
d. ultrasonic bath

Good luck!