Chapter 4 Flashcards
What is light
Light is radiant energy, a stream of particles called photons, does not need a medium to travel through.
Does the speed of light reduce through vacuum
No, the speed of light does not reduce in a vacuum. It only slows down when they pass through an object.
What is the speed of light
Almost 300k km/s.
What can light sometimes also be described as
It can be described as a wave of changing electric and magnetic energy.
What does the energy a photon Carries depend on
It depends on the frequency and wavelength
What are the colors the human eye is sensitive to called
The visible spectrum
What does the visible spectrum rely on
The wavelength of light received by the eye
What is the measurement between wavelengths
Nanometers
What is the longest and shortest visible wavelength humans can see
Red=700 nanometers and violet=400 nanometers
What is frequency
Frequency is the number of wave crests (top points) that pass a given point in 1 second
What is period
It is the time change between passage of successive crests
What is white light
White light is a mixture of all colors and wavelengths. A prism can separate these
What is the electromagnetic spectrum composed of
It is composed of radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma rays
What is infrared radiation
Discovered by William Herschel, it is the heat radiation related to visible light
What is ultraviolet light
Discovered by j.Ritter, it is absorbed by the atmosphere and is responsible for sunburns. It is just beyond the violet end of the visible spectrum.
What are radio waves
They were predicted by maxwell and produced by hertz, they are used to discover a wide range of astronomical processes and are used for communication, microwave ovens, and search for extraterrestrials
What are x-rays
They were discovered by roentgen, used by doctors to scan bones and organs, used by astronomers to detect black holes and tenuous gas in distant galaxies
What are gamma rays
A region of rays relatively unexplored, atmosphere absorbs the entire region, sometimes relieve bursts of gamma ray radiation from deep space
What are the energy levels of long and short frequencies
Short wavelength = high frequency = high energy
Long wavelength = low frequency = low energy
What is the kelvin temperature scale
It is a scale that relates to an objects molecular movement, as it is cooled the molecular motion comes to a halt and it’s energy approaches zero
How do hotter bodies radiate at short wavelengths
Hotter bodies radiate more strongly at shorter wavelengths
What is a black body
A black body is an object that absorbs all radiation and heat falling on it
What happens if a black body is heated
It radiates more efficiently than any other kind of object. They are excellent absorbers and emitters.
What is the structure of an atom
Nucleus=composed of densely packed neutrons and positively charged protons
Cloud of negative electrons= held in orbit around nucleus by positive charge of protons
What is an element
It is a substance composed of only atoms that have the same number of protons in their nucleus
What are the chemical properties of an element determined by
Their number of electrons
When does an atoms energy increase
When an electron moves to an outer orbit, it is said to be excited
When does an atoms energy decrease
When an electron moves to the inner orbit
What is conservation of energy
It is the fact that energy change in an atom must be compensated elsewhere
What are two ways to preserve energy conservation
Absorption and emission of EM radiation
What is spectroscopy
It is capturing and analyzing a spectrum
What is the role of spectroscopy
Allows the determination of the composition and conditions of an astronomical body, it assumes every atom has a unique spectral signature
What are the 3 types of spectra
Continuous,emission-line, and dark-line/absorption-line
What is continuous spectrum
It is the spectra of a black body, they are typically solids and dense gasses
What is emission-line spectrum
It is produced by hot,tenuous gas. Some examples are fluorescent tubes, aurora, and interstellar clouds
What is dark-line / absorption-line spectrum
Light from black body that passes through cooler gas, lines of the sun is an example
What wavelengths penetrate the atmosphere
Radio waves, visible light, some infrared.
Why do some wavelengths penetrate the atmosphere
It happens through atmospheric windows, which are wavelength regions with high transparency
What is the Doppler shift in sound
If a sound has short wavelengths it is higher pitched, if it has long wavelengths it is lower pitched. If the source of the sound is moving the pitch changes
What is Doppler’s shift in light
If a source of light is in motion relative to the observer, it’s spectral lines shift to new wavelengths. Shorter wavelengths is called blueshift and longer wavelengths is called redshift
What is Doppler shift used for
It is used to determine an object’s velocity
