Physical Science Module 15

Front 1

wave theory of light

Back 1

Theory by Christian Huygens which stated that light behaves as a wave. Refined by Maxwell, who showed that the wave of light consisted of transverse waves of oscillating electric and magnetic fields perpendicular to each other.

Front 2

particle theory of light

Back 2

Theory by Newton which states that light is composed of little packets (photons) in a constant stream, which act like particles.

Front 3

quantum-mechanical theory of light.

Back 3

light has a dual nature, composed of little packets of waves, thus acting like particles and waves.

Front 4

electromagnetic wave

Back 4

A transverse wave composed of an oscillating electric field and a magnetic field that oscillates perpendicular to the electric field.

Front 5

speed of light in air

Back 5

300,000,000 m/sec.

Front 6

Does the speed of light depend on temperature?

Back 6

No. It only depends on the medium it is traveling through. Light travels fasted through air, then liquid, then solids.

Front 7

Einstein's Special Theory of Relativity

Back 7

Nothing with mass can travel faster than the speed of light in a vacuum.

Front 8

Name the order of color in visible light, from longest wavelength to shortest

Back 8

Red, Orange, Yellow, Green, Blue, Indigo, Violet

Front 9

electromagnetic spectrum

Back 9

The range of wavelengths of electromagnetic waves. From shortest to longest, these are: gamma rays, x-rays, UV rays, visible light, infrared light, microwaves, TV waves, and radio waves.

Front 10

What are gamma rays, x-rays, and UV rays known for?

Back 10

They all have enough energy to damage or destroy living tissue. Too much exposure to these types of rays is dangerous.

Front 11

What is infrared light known for?

Back 11

It gives off its energy mostly as heat.

Front 12

What is special about microwaves?

Back 12

Microwaves are absorbed by water in food, which vibrate and cause friction with the molecules in the food, heating them.

Front 13

What two things happen when light hits an obstacle?

Back 13

Light is reflected (bounces off) and refracted (transmitted through.)

Front 14

The Law of Reflection

Back 14

The angle of reflection equals the angle of incidence.

Front 15

When light refracts into a substance in which it must slow down,

Back 15

the light ray will bend toward a line perpendicular to the surface it strikes.

Front 16

When light refracts into a substance in which it speeds up,

Back 16

the light ray will bend away from a line perpendicular to the surface it strikes.

Front 17

How does a rainbow form?

Back 17

Light enters a water droplet, where it is refracted. The different wavelengths are refracted to varying degrees, so there is some separation of the colors. The light is reflected off the back of the droplet, then refracts further when it exits back out the front of the droplet. By this point, the different wavelengths (colors) are separated enough to be visible.

Front 18

Red light refracts the least in a rain drop, so it exits out lowest of all the colors from the drop. Why is it seen in the highest position in the rainbow?

Back 18

While every raindrop refracts out every color, our eyes are only in position to see certain colors from certain raindrops. The raindrops higher in the sky will have their red rays hit our eyes; the other colors will pass over our heads. The raindrops slightly lower in the sky will have their green rays hit our eyes. The violet rays will still pass over our heads, and the red rays from that drop will hit lower on our body (not our eyes.) Still lower in the sky, raindrops will have their violet rays hit our eyes, while both the green and red rays will hit below our eyes on the ground. Therefore, even though the red rays exit out the lowest part of any particular rain drop, they are seen by our eyes from drops that are higher in the sky.

Front 19

What conditions must exist in order for a rainbow to form?

Back 19

The sun must be behind you, rain must be in front of you, and the sun must be fairly low in the sky.

Front 20

What does a converging lens do to light?

Back 20

It focuses light into a focal point beyond the lens.

Front 21

What does a diverging lens do to light?

Back 21

It scatters light beyond the lens.

Front 22

How are the edges of a converging lens shaped?

Back 22

They are convex outward.

Front 23

How are the edges of a diverging lens shaped?

Back 23

They are concave outward.

Front 24

How does the eye see color?

Back 24

The retina in the back of the eye contains cells (cones) that are sensitive to particular frequencies of light. There are red cones (sensitive to low frequencies), green cones (mid frequencies), and blue cones (high frequencies.) When light of that frequency hits a cone, it sends a signal to the brain, which interprets that particular color as being present at that spot.

Front 25

What kind of glasses lens does a near-sighted person need?

Back 25

Near-sightedness results from the lens focusing light too well, such that the focal point falls before the retina. A diverging lens is used to scatter the light out a bit before it hits the eye lens, making the eye lens work harder and moving the focal length back onto the retina.

Front 26

What kind of glasses lens does a far-sighted person need?

Back 26

A far-sighted eye has a lens that doesn't focus well enough, making the focal point fall past the retina. A converging lens is necessary to help focus the incoming light a bit before it hits the eye lens so that the light can be focused by the time it reaches the retina.

Front 27

Is light color additive or subtractive?

Back 27

Light color is additive, with white light resulting from the mix of all different light colors together.

Front 28

Is pigment color additive or subtractive?

Back 28

Pigment color is subtractive, absorbing (subtracting) all light wavelengths other than the "color" of the pigment. This color is reflected back to the eye and perceived as the color of the pigment. Black pigment "subtracts" all wavelengths, resulting in no reflected light back to the eye.