Lesson 5 Flashcards
Power
Rate of energy flow in watts
1 watt = 1 joule/s
Which colours are directly detected by cells in our eyes (primary colours of vision)?
Red
Blue
Green
Four basic ways light interacts
- Emission (light comes from electric potential energy)
- Absorption
- Transmission
- Reflection/scattering
Basic properties of waves
- Wavelength; distance between peaks or troughs
- Frequency; number of peaks passing each second (Hz)
- Speed; how fast energy travels from one place to another
Wavelength x Frequency = speed
Light is an ____
electromagnetic wave (electrons move when light passes by)
What is the speed of light?
C = 300,000 km/s
Relationship between wavelength and frequency
longer the wavelength = lower frequency and vice versa
Photons
individual particle of light
- characterized by wavelength and frequency
Relationship between wavelength and energy of photon
Shorter the wavelength (or high it’s frequency) = higher energy of photon
Electromagnetic spectrum
complete spectrum of light
From highest energy/shortest wavelength/lowest frequency:
Gamma rays, X rays, Ultraviolet, Visible, Infrared, Radio waves, microwaves
Visible light
400-700 nm
Blue (short wavelength = high frequency = high energy) - Red (long wavelength = low frequency = low energy)
Atomic number
number of protons
Atomic mass
protons + neutrons
Isotopes
same #protons but different neutrons
Ex: Carbon 12 is 6 and 6, Carbon 13 has 7 neutrons, Carbon 14 has 8
Plasma
hot gas which atoms have become ionized (stripped of electrons)
Pressure
force per unit area pushing on an object’s surface
Atoms contain energy in three ways:
- Mass energy (E=mc^2)
- Electrical potential energy (depends on arrangement of electrons around nuclei)
- Kinetic energy (motion)
Electron’s energy levels
Electrons can only have particular amounts of energy
- Energy levels
- Ground state = O eV
- Excited states go higher levels depending on the atom
- Cannot be between levels; if has enough energy to get them halfway to the next level, will only go to the next possible level
- Ionization level = electron exits atom
Spectroscopy
process of obtaining spectrum and reading information
Continuous spectrum
broad range of wavelengths without interruptions
Emission line spectrum
Emission lines against a black background
Emission lines depend on low-density cloud of gas composition and temperature
Absorption line spectrum
dark absorption lines against rainbow background
Cloud of gas lying between us and light bulb (and cloud cooler than bulb or light source); we can’t see what the cloud absorbed
