General Physics 2

radio and tv waves

accelerating charges

Communications remote controls

MRI

Requires controls for band use

microwave

Accelerating charges & thermal agitation

Communications, ovens, radar

Deep heating

Cell phone use

infrared

Thermal agitations & electronic transitions

Thermal imaging, heating

Absorbed by atmosphere

Greenhouse effect

visible light

Thermal agitations & electronic transitions

All pervasive

Photosynthesis, Human vision

ultraviolet

Thermal agitations & electronic transitions

Sterilization, Cancer control

Vitamin D production

Ozone depletion, Cancer causing

x-rays

Inner electronic transitions and fast collisions

Medical Security

Medical diagnosis, Cancer therapy

Cancer causing

gamma rays

Nuclear decay

Nuclear medicine, Security

Medical diagnosis, Cancer therapy

Cancer causing, Radiation damage

transparent

If the material is _ to the particular

frequency, then the wave can largely be

transmitted.

opaque

If the material is _ to the frequency, then

the wave can be totally reflected.

absorbed

The wave can be_ by the material,

indicating that there is some interaction

between the wave and the material, such as the

thermal agitation of molecules.

radio and tv waves

• is defined to contain any electromagnetic wave produced by

currents in wires and circuits.

• carrier of audio information

amplitude modulation

AM

frequency modulation

FM

50 or 60hz

The lowest commonly encountered radio

frequencies are produced by high-voltage AC

power transmission lines at frequencies of

extremely low frequency

radio waves of

about 1 kHz are used to communicate with

submerged submarines.

AM radio waves

are used to carry commercial

radio signals in the frequency range from 540

to 1600 kHz.

FM radio waves

are also used for commercial

radio transmission, but in the frequency range

of 88 to 108 MHz.

electromagnetic waves

Astronomers and astrophysicists collect signals from outer

space using

pollution

A common problem for astrophysicists is the _

from electromagnetic radiation pervading our surroundings

from communication systems in general.

microwaves

• are the highest-frequency

electromagnetic waves that can be produced by

currents in macroscopic circuits and devices.

• Microwave frequencies range from about 109

  Hz to the highest practical LC resonance at

  nearly 1012 Hz.

• short wavelengths

• produced by accelerating electrons

radar

is a common application of microwaves that was

first developed in World War II.

doppler shift

be used to

determine the speed of a car or the intensity of a

rainstorm.

sophisticated radar systems

used to map the Earth

and other planets, with a resolution limited by

wavelength.

infrared radiaion

radiation is generally produced

by thermal motion and the vibration and

rotation of atoms and molecules.

• means “below red”

night-vision scopes

can detect the infrared

emitted by various warm objects, including

humans, and convert it to visible light.

reconnaissance satellites

can detect

buildings, vehicles, and even individual

humans by their infrared emissions, whose

power radiation is proportional to the fourth

power of the absolute temperature.

visible light

is the narrow segment of the

electromagnetic spectrum to which the

normal human eye responds.

• produced by vibrations

red light

has the lowest frequencies

and longest wavelengths,

violet

has the highest frequencies and

shortest wavelengths.

blackbody radiation

peaks in the visible part of the

spectrum but is more intense in the

red than in the violet, making the Sun

yellowish in appearance.

optics

is the study of the behavior of visible

light and other forms of electromagnetic

waves.

ray optics

is the study of such situations

and includes lenses and mirrors.

ultraviolet radiation

• “above violet”

• extend upward from violet, the

  highest-frequency visible light.

• also produced by atomic and

  molecular motions and electronic transitions.

uv a

320-400nm

uv b

290-320nm

• causes skin cancer

uv c

220-290nm

x-rays

• This radiation was called an _, because its identity

and nature were unknown.

• have adverse effects on living cells similar to

those of ultraviolet radiation, and they have the

additional liability of being more penetrating,

affecting more than the surface layers of cells.

gamma rays

• The most penetrating nuclear radiation

• an extremely high frequency electromagnetic wave.

• are any electromagnetic radiation emitted by a

  nucleus.

• identical to X-

  rays of the same frequency—they differ only in

  source.

light

is an electromagnetic radiation that has

properties of waves and particles.

echo

is a reflected sound wave.

refraction

is the bending of light as it

passes from one medium to another.

images

are formed when light

strikes a reflecting surface, such

as mirror or lens.

mirrors and lenses

are very

essential in our daily living.

cornea

You can see because of the _

lens of your eye.

plane mirrors

The flat mirror that we can see

everywhere.

When light strike a plane mirror, the light

rays obey the law of plane mirror

concave mirror

a mirror that

curves inward like a hollow inside a

sphere. The light hitting the surface of a

concave mirror that converges.

convex mirror

a mirror that

curves outward, like outside of a sphere.

It diverge the light and creating only

virtual image.

center of curvature (C)

center of the circle

focus (F)

one-half of the radius

vertex (V)

the point where the mirror crosses

the principal axis.

principal axis

a line drawn through the

vertex.

focal length (f)

the distance from the focus

to the vertex of the mirror

radius of curvature

the distance between the

center of curvature to the vertex of the mirror.