3.4 Nature of Light Flashcards
3 ways quantum mechanics form the foundation of chemistry
- explains the periodic table
- explains the behavior of elements in chemical bonding
- provides a practical basis for lasers, computers, and other applications
wave-particle duality of light
lights can have properties of both waves and particles
speed of light
3.00 x 10^8 m/s
amplitude
height of the wave
determines light’s intensity or brightness
high amplitude = bright light
high amplitude = more force
wavelength
distance between adjacent crests or troughs
short wavelength = high frequency
symbol for wavelength
upside down y (lambda)
wavelengths are measured in:
m, um, nm
frequency
number of cycles (wave crests) that pass through a point per unit of time
high frequency = more total force
high frequency = short wavelength
symbol for frequency
v
frequency is measured in:
cycles/s (s^-1)
Hertz (Hz)
equation for frequency
v = c / lambda
color of light is determined by:
wavelength/frequency
colors in the spectrum of light
red
orange
yellow
green
blue
indigo
violet
how do we see color?
an object absorbs some of the wavelengths of white light and reflects others, it appears colored (the reflected wavelengths are the colors we see)
what is the color with the longest wavelength?
red
what is the color with the shortest wavelength?
violet
electromagnetic spectrum
spectrum of visible light that comprises a small fraction of all wavelengths of light
what wave has the lowest energy?
radio waves
what wave has the highest energy?
gamma rays
order of the electromagnetic spectrum
radio
microwave
infrared
visible light
ultraviolet
x-ray
gamma ray
interference
interaction between waves
constructive interference
waves interact so that they add to make a larger wave while in phase
forms one wave with a high amplitude
destructive interference
waves interact so they cancel each other out while out of phase
forms a line
diffraction
traveling waves encounter an obstacle or opening in a barrier that is about the same size as the wavelength
waves bend
particles do not diffract
interference pattern
diffraction of light through two slits separated by a distance comparable to the wavelength
destructive interference -> dark areas
constructive interference -> light areas
photoelectric effect
metals emitting electrons when light hits their surface
classic wave theory
-attributed this effect to the light energy being transferred to the electron
-shorter wavelength/brighter intensity = more electrons ejected
-predicts dim light = lag time
threshold frequency
minimum frequency was needed before electrons would be emitted regardless of the intensity
quanta/photons
proposal by Einstein that light came in packets
the energy of a photon of light is proportional to:
frequency
(inversely proportional to wavelength)
planck’s constant equation
h = 6.626 x 10^-34 Jxs
energy equations
e = hv
e = hc/wavelength
