Basics of Light

7/29/2019 Basics of Light

1/21


2/21

Light Fundamentals: Slides 3-8

Light and Matter: Slides 9-13

Reflection and Refraction of Light: Slides

14-16

Practice Problems Slides 17-18


3/21

Light is the range of the frequencies of electromagneticwaves that stimulates the retina of the eye.

Light waves have wave lengths from about 400nm

(violet light) to 700nm (red light).

Colors of the spectrum change from violet, indigo,

blue, green, yellow, orange, and then red.


4/21

Light travels in a straight line, also called aRay. Galileo was the first to hypothesize that light has a finite speed.

Danish astronomer Ole Roemerwas the first to determine thatlight does travel with a measurable speed.

American physicist Albert A. Michelson measured the timerequired for light to make a round-trip between two Californianmountains 35km apart and became the first American to

receive the Nobel Prize in 1926.


5/21

The speed of light is equal to: = c The frequency of light can be counted with

extreme precision using lasers.

In 1983 the International Committee on

Weights and Measurements defined the speed

of light to be 3.00 x 108 m/s


6/21

ALuminous body emits light waves, such as theSun.

An Illuminated body simply reflects light wavesproduced by an outside source, such as the

Moon.


7/21

The rate at which visible light is emitted from a

source is called the Luminous Flux, P. The unit of Luminous Flux is the Lumen, lm. The Illuminance, E, is the rate at which light

falls on a surface, which is measured in lumens

per square meter, lm/m2.


8/21

The Luminous Intensity of a point source is theluminous flux that falls on lm2 of a sphere 1m

in radius.

Candela, cd, is another unit of measurementused in Luminous Intensity.


9/21

Transparent materials can transmit light waveswithout distorting images.

Translucent materials can transmit light but do notpermit objects to be seen clearly through them.

Opaque materials transmits no light but absorbs orreflects all light.


10/21

Newton discovered the Spectrum, which is theordered arrangement of colors from violet to

red.

The Additive Color Process is when differentcolor lights combine to form a new color.


11/21

Primary colors are the three basic colors; redlight, green light, and blue light that combines to

form new colors.

Secondary Colors are those formed when theprimary colors are combined, such as yellow,

cyan, and magenta.


12/21

Complementary Colors combines and formswhite.

Yellow and blue, cyan and red, magenta and green

are all Complementary Colors.

ADye is a molecule that absorbs certainwavelengths of light and transmits or reflects

others.


13/21

APigment is a colored material that absorbs certain colors andtransmits or reflects others.

A pigment particle is larger than a dye and can be seen with a

microscope.

APrimary Pigment absorbs only one primary color from white light,such as yellow.

ASecondary Pigment absorbs two primary colors and reflects one,such as red, green, and blue.


14/21

The law of Reflection states that the angle of reflection is

equal to the angle of incidence.

Refraction is the bending of light rays at the boundary

between two media. Refraction occurs only when the

incident ray strikes the boundary at an angle.

When light goes from a medium with a small n to one

with a large n, it is bent toward the normal.

Reflection and Refraction of Light


15/21

Snell's Law states that when visible light enters a

transparent material at an angle, the direction of the light

is refracted or bent at a different angle.

Light waves of different wavelengths have slightly

different refractive indices. Thus, they are refracted at

different angles. Light falling on a prism is dispersed into

a spectrum of colors.



16/21

Total internal reflection occurs when light is

incident on a boundary from the medium with

the larger index of refraction. If the angle of

incidence is greater than the critical angle, no

light leaves; it is all reflected.



17/21

Practice Problem

Use Snell's law, the sine button on your calculator, a protractor, and the

index of refraction values to complete the following diagrams. Measure,

calculate, and draw in the refracted ray with the calculated angle of

refraction.


18/21

Solution

Given: ni = 1.00nr = 1.33 = 45 degrees

Find: Theta r = ???

Third, list the relevant equation:

Fourth, substitute known values into the equation and algebraically manipulate the

equation in order to solve for the unknown variable - "theta r."

1.00 * sine (45 degrees) = 1.33 * sine (theta r)0.7071 = 1.33 * sine (theta r)

0.532 = sine (theta r)

sine-1 (0.532) = sine-1 ( sine (theta r))

32.1 degrees = theta r


19/21

LASERS!!!!!!


20/21

Zitzewitz, Paul W. "Light." Glencoe Physics:

Principles & Problems. Glencoe, 1999.

Zitzewitz, Paul W. Reflection and

Refraction." Glencoe Physics: Principles &

Problems. Glencoe, 1999.

Bibliography


21/21

Thank You!!!!!!

Basics of Light

Documents

Transcript of Basics of Light