Urban and Civil

Nov 16, 2013 (4 years and 6 months ago)

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particles or waves of energy emitted

energy released from
all objects

energy released when a
nucleus of an atom changes

Energy emitted from all atoms when
electrons move to different energy levels
in an atom

Energy is not matter it is a wave

Ionizing

produces ions

(alpha, beta, gamma)

Non
-

doesn’t produce ions

Visible Spectrum

Waves can be described in terms of four characteristics

Amplitude

Wavelength

Frequency

speed

Wavelength

is distance between crests:

measured in m, cm, mm,

m, nm, etc.

Amplitude

is the height of wave: Intensity of light depends on amplitude

measured in m, cm, mm,

m, nm, etc.

Frequency

is how fast the wave oscillates up and down:

measured in cycles/sec. Also called a Hertz (Hz): 1/sec or sec
-
1

Speed

is the speed of light: 3.00 X 10
8

m/s c

Calculate

Green light has a wavelength of 570 nm.
What is it’s frequency?

What is the color of light that has a
frequency of 4.7 x 10
14

1/sec?

(look in book for color)

Energy, frequency and wavelength

are related

E= h

h= Planck’s constant

6.6262 X 10
-
34
Js

Calculate

A certain violet light has a wavelength
of 413nm. What is the frequency of the
light? What is the energy of the light?

㴠振

†††

㴠振

Convert nm to m

=
3.00X 10
8
m/s

= 7.26 X 10
14

1/s

413 X 10
-
9
m

E= h

E=(6.6262 X 10
-
34

Js)(7.26 X 10
14
1/s)

= 4.81 X 10
-
19
J

Light

Is a form of electromagnetic radiation

Has dual properties

Behaves like a
wave
. Moves through space
in waves

Behaves like a stream of
particles

called
photons

Light is

quantized

has a specific energy

Wave nature of light

Oscillating electromagnetic fields

Nuclear binding energy

E=mc
2

Mass is converted to energy

Mass proton=1.0078 amu

Mass of neutron=1.0087 amu

1J=1 kg m
2
/sec
2

1 amu=1.66 x 10
-
27

kg