Light + Electromagnetic spectrum

its cooked

Optics

the study of light and its properties

Spectograph

a device for separating light from a source into its component

Newton claimed light was made of

particles

Christiaan Hughes claimed light was made of

waves

difference between particle and wave behavior

Particles can be in only one place at a time, whereas waves can spread over extensive space

Wavelength

the distance between successive peaks or troughs of a wave

Frequency

The number of peaks and troughs of a wave that pass a point in space in a single second (Hertz)

Amplitude

a measure of a wave’s strength equal to half wave’s total height

the shorter the wavelength

the higher the frequency (more waves pass in a given time)

wave speed

the distance an individual peak travels in one unit of time

all light waves move at the same speed when

moving through a vacuum

light is composed of

electromagnetic radiation

electromagnetic radiation

oscillating electric and magnetic fields travelling through space

visible light

the form of light to which the human eye responds, 400nm-700nm

Electromagnetic spectrum

the full range of electromagnetic radiation at different wavelengths, from gamma rays (very short) to radiowaves (very long)

longest wavelength visible light

Red light, about 700nm

Our eyes respond to

yellow-green light, about 550nm

shortest wavelength visible light

Violet light, about 480nm

Radiowave

wavelength longer than o.1m

microwave

shortest wavelength radiowave

Infrared wave

heat

ultraviolet light

causes sunburns

Gamma rays

kills cancer cells

White light

light from the sun

Refraction

the bending of light as it passes from one transparent medium to another

spectrum

the distribution of light intensity versus wavelength or frequency

intensity

the energy of light that an object emits, either in total or at a specific wavelength

Kirchhoff’s first law

an opaque body emits a continuous spectrum

Kirchhoff’s second law

relatively hot, low density gas emits a sequence of bright spectral lines, called emission lines

Kirchhoff’s third law

Relatively cold, low density gas in front of a hotter, opaque body produces a continuous spectrum with dark spectral lines superimposed, called absorption lines

Energy

the ability to perform work

kinetic energy

due to an object’s bulk motion

gravitational potential energy

possessed by an object because of its position in a gravitational field

heat

transfer of thermal energy

thermal energy

due to random motions of atoms

temperature

a measure of the average kinetic energy of all particles in a substance

temperature is measured in

Kelvins (K)

conservation of energy

the principle whereby total energy remains constant in a system or process in which energy is not added or removed, even though the energy can be converted from one form to another

blackbody radiation

electromagnetic radiation from a dense, opaque body whose spectrum depends only on the body’s temperature

Quanta

tiny bundles of photons

photons

particles of light

Wein’s law

the mathematical relationship between a blackbody’s temperature and the wavelength at which it radiates with peak intensity

hotter objects peak at

lower wavelengths

Luminosity

A light source’s total energy output per unit of time

Nebula

interstellar cloud of dust, hydrogen, helium, other ionized gasses

Stefan-Boltzwann law

the mathematical relationship between a blackbody’s luminosity and its surface area and temperature

hotter, larger objects glow

more brightly

photons can function as both

particles and waves

ground state

the lowest energy state of an atom

excited state

higher energy

emission

the release of a photon of a specific wavelength when an electron jumps from a higher to a lower energy level

absorption

the capture of a photon of a specific wavelength, causing an electron to jump from a lower to a higher energy level

energy differences in orbits must equal

the energy of the emitted photon

Lyman series

Emission or absorption lines of the hydrogen atom as an electron moves between the ground and excited states

Balmer series

Emission or absorption lines of the hydrogen atom as an electron moves between the first excited state and higher

Doppler shift

a change in wavelength that results because either a wave source or an observer moves relative to one another

Redshifted

an increase in the wavelength of light that results when the light source moves away from the observer or vice versa

all electromagnetic radiation travels at

the same speed