Chapter 13 Section 3
-Quantum mechanical model grew out of the
study of light
-light consists of electromagnetic radiation
-includes radio and UV waves, X-rays,
gamma rays, visible light
-these waves move at a constant speed of
3.00X108m/s or 3.00X1010cm/s
-this is the speed of light (c)
origin
amplitude- height of a wave from the origin to
the crest
wavelength- (λ) - distance between two adjacent
crests (units= m, cm, nm)
frequency- (ν) - # of wave cycles that pass
through a given point per unit time
-(units= cycles/sec or 1/s or s-1 or hertz- Hz)
-each complete wave cycle begins at the origin
and returns to the origin
-frequency is directly proportional to the speed at
which the wave is traveling- the faster the
wave, the higher the frequency
-frequency and wavelength are inversely
proportional
visible light- light that can be seen by the human
eye
-wavelength determines the color of the visible
light
-can see colors when white light is passed
through a prism
-red, orange, yellow, green, blue, indigo, violet
-red light has the longest wavelength (750nm)
-violet has shortest (400nm)
-electrons emit light when they are excited by the
passage of an electric discharge through an
element
atomic emission spectrum- range of
wavelengths emitted by a particular element
that can be used to identify an element
Ex- neon lights
Formulas
c = νλ
c = speed of light (3.00 x 108m/s or
3.00X1010cm/s)
ν = frequency (1/s, s-1, Hz)
λ = wavelength (m, cm, nm(10-9))
λ = c/ν
Book problems
ν = c/λ
Max Planck
-found that energy of a body changes in small
discrete units
E = hν
E = energy in joules (J)
h = Planck’s constant = 6.6262 x 10 -34J∙s
ν = frequency (1/s, s-1, Hz)
v = E/h
photons- particles of light
photoelectric effect- metals emit electrons when
light shines on them
*especially the alkali metals
-used in solar calculators