Lesson 5 Flashcards
Why is light a form of energy? What type of energy is it?
Light is a form of energy because it has warmth
- the energy that light carries is radiative energy
What are scientists more interested when it comes to measuring the energy of light?
They are interested in the rate that light transfers energy rather than the total energy it carries
What is power? What is the unit measured?
Power is the rate of energy flow
- it is measured in watts
What does white light consist of?
White light is made up of all the other colours (sunlight is white light)
What does the colour black signify?
Black is the absence of light or colour
What four things can matter do to light when it interacts with it?
- emission - comes from a matter emitting radiative energy or a light emitting radiative energy
- absorbtion - absorbed energy from light causes skin to warm
- transmission - re-emission of energy
- reflection - light bounces a) in the same direction or b) scattered
What are the three properties of a wave?
- it has a wavelength (the distance between two peaks)
- it has frequency (the number of times per second a wave goes up and down)
- speed (how fast the peaks travel)
What is a particle?
A rigid body of mass
What is a wave?
A repetitive motion of non-solid substances (water or air)
How are light and gravity analogous?
Because the are both energy emitted from a source
What is the emission source of gravity?
Matter
What is the emission source of light?
Charge
What is a photon?
A particle of light
When do electrons move?
When light passes by - light carries a vibrating electric field
How fast do electromagnetic waves travel?
At the speed of light
What is the formula for the speed of light?
speed of light (c) = wavelength x frequency
What does a longer wavelength mean?
A lower frequency
What does a shorter wavelength mean?
A higher frequency
What is Planck’s constant? What is it measured in?
It measures the energy of light
- It is the units of joules per second
What is the highest frequency found in nature? What part of the spectrum does this frequency belong to?
The highest frequency is a zetahertz
- these are gamma rays
What is the range of frequencies visible to humans?
400nm (blue) to 700nm (red)
What is the order of frequencies in the light spectrum, going from the highest frequency to the lowest?
gamma rays - x-rays - UV - visible light - infrared - microwaves - radio waves
Who first proposed the idea of the atom?
Democratus
What are atoms composed of?
Protons, neutrons, and electrons
What two properties to particles have?
They contain both mass and charge
What two units does charge come in?
Positive and Negative
What are the two properties of charge?
Charges cannot be cut (ex. you cannot have 0.5 positive charge) and oppositely charged particles attract, while similarly charged particles repel
What property does every atom of a given element have?
They all have the same number of protons, but the numbers of their electrons can vary
How do atoms and molecules interact with each other?
Through strong and weak forces
What three phases of can matter take on?
- solid phase: atoms are rigidly locked together by mutual forces
- liquid phase: atoms experience a net force with spring-like characteristics
- gas phase: atoms are free to move around as if free from any net force
What is an atomic number?
the number of protons in a nucleus
What is an atomic mass number?
the number of protons and neutrons in an atom
What is a molecule?
Two or more atoms
What is an isotope?
The same number of protons but a different number of neutrons
What is sublimation?
Vaporization from a solid
What is evaporation?
Vaporization from a liquid
What is molecular dissociation?
When collisions become so violent in the atom (at high temperatures) that the chemical bonds that hold them together are broken
What is ionization?
The process of stripping electrons from atoms
Why do phases of the same material (ex. hydrogen) behave differently?
Because of the difference in their chemical bonds
What is plasma?
It is a type of hot gas in which atoms have become ionized
What are the two factors for determining what phase a substance takes?
Temperature and pressure
What is pressure?
the force per unit area pushing on an object’s surface
What is spectroscopy?
The process of obtaining and reading a spectrum
What are the three basic types of spectra?
- continuous spectrum - the spectrum that spans all possible wavelengths without interruption
- emission spectrum - a thin or low-density cloud of gas emits light only at specific wavelengths that depend on its composition; it produces a spectrum with bright emission lines
- absorption spectrum - a cloud of gas between us and a lightbulb can absorb light of specific wavelengths, leaving dark absorption lines in the spectrum
What is a chemical fingerprint?
the spectrum of light produced by a material (due to its specific properties)
What is a blackbody?
An object that can absorb light but from which light cannot easily escape
What does a blackbody’s thermal radiation depend on?
Only on temperature
What are the properties of dense objects like stars?
They all behave as blackbodies
What happens when a blackbody heats up?
there is an increased accumulation of photons, so it radiates energy as thermal radiation (blackbody radiation) and it changes colour (from red to white hot)
What do the laws of blackbody radiation describe?
How light changes with colour
What are the two laws of blackbody radiation?
- hotter objects emit more radiation per unit surface area at every wavelength
- hotter objects emit more of their light at shorter wavelengths (high energy)
What is the doppler effect?
The observation that an object’s pitch (in the auditory modality) changes as a function of its distance from us
Does the doppler effect exist in the frequency of light? How is it measured?
Yes
- it is measured from shifts in the wavelengths of spectral lines
What wavelength does an object moving towards us have?
A blue shift (a shift to blue from the lab)
What wavelength does an object moving away from us have?
A red shift (a shift to red from lab)
What is the only information a doppler effect can give us?
The speed at which an object is moving towards us or away from us (not anything other than towards or away)
