Slide Review Flashcards
Review Slides
What is light?
Light is electromagnetic radiation.
What is the range of wavelengths for visible light?
Wavelengths of visible light range from 400 nm (violet) to 700 nm (red).
How long is 1 nanometer (nm) in meters?
1 nanometer (nm) = 10⁻⁹ meters.
How does visible light compare to other types of radiation in terms of wavelength?
Other types of radiation have either longer or shorter wavelengths than visible light.
Does light travel at different speeds depending on its energy or wavelength?
No, all light travels at the same speed, regardless of its energy or wavelength.
What is the speed of light in a vacuum?
The speed of light is 300,000 km/s (kilometers per second).
What is the significance of the speed of light in the universe?
The speed of light is the fundamental speed limit of the universe; nothing can travel faster than light.
What is light described as?
Light is a wave
How do we describe light waves?
We describe light waves by their wavelength, which is the distance between wave crests.
What symbol is used to represent wavelength?
The Greek letter λ (lambda) is used to represent wavelength.
What else can be used to describe light waves besides wavelength?
We can describe light waves by their frequency, the number of waves that pass a point each second.
What are the units of frequency?
The units of frequency are Hertz (Hz
What is 1 Hertz equivalent to?
1 Hertz (Hz) is equivalent to 1/second.
How are wavelength and frequency related?
Wavelength and frequency are directly related. The wavelength (λ) depends on how many crests of a wave pass in a given time
What is the wavelength if 1 wave crest passes each second?
If 1 wave crest passes each second (frequency = 1 Hz), the wavelength is 300,000 km, which is the distance light travels in one second.
How is the wavelength (λ) calculated for a wave?
The wavelength (λ) is the distance between crests. For a frequency of
𝑓 crests per second, the wavelength is related to the speed of light by the formula: 𝜆= c/f, where 𝑐 is the speed of light.
What is the relationship between frequency and time between crests?
The time between crests T is the inverse of frequency, i.e. T = 1/f
Do astronomical objects produce radiation across the full electromagnetic spectrum?
Yes, astronomical objects emit radiation across the full electromagnetic spectrum, from very high frequency gamma rays to very low frequency radio waves. Astronomers observe light at all wavelengths to study these objects.
Why do objects emit light? What role does temperature play?
Objects emit light for many reasons, and one key reason is temperature. Temperature measures how fast atoms or molecules move.
Hot objects: Atoms move fast and can emit more light.
Cold objects: Atoms move slowly.
The lowest possible temperature, when atoms stop moving altogether, is absolute zero: -273°C (-459°F).
What is thermal radiation (blackbody radiation), and how does temperature affect it?
Thermal radiation, or blackbody radiation, produces a continuous spectrum, emitting some radiation at all wavelengths.
Key Points:
Hotter objects emit more radiation at all wavelengths.
The radiation from hotter objects peaks at shorter wavelengths.
What is the relationship between the average wavelength of light emitted by a hot object and its temperature?
The average wavelength of light (𝜆) emitted by a hot object is inversely related to its temperature (T). The formula is:λ=3×10^6/T nm
Where lambda is measured in nm and T is in kelvin
What is the peak wavelength of radiation emitted by a city with a temperature of 27°C (300 K)? What part of the light spectrum is this in?
Using the formula,λ=3×10^6/T nm, we get λ=3×10^6/300 = 10,000 nm
This means the peak wavelength of radiation emitted is 10,000 nm, This is also in the infrared part of the spectrum
A star has a temperature of 6000 K. What is the peak wavelength of the light it emits?
500 nm
A star emits light with a peak wavelength of 300 nm. What is the temperature of its surface?
10,000 K
What happens when an electron absorbs light?
When an electron absorbs light, it moves from a closer orbit to a more distant orbit. The energy of the light excites the electron to a higher energy level.
What happens when an electron emits light?
When an electron moves from a more distant, higher energy orbit to a closer, lower energy orbit, the energy difference between the two orbits is emitted as light.
shorter wavelength = ?
higher energy
Longer wavelength = ?
lower energy
What wavelengths of light do atoms emit and absorb?
Atoms emit and absorb only the wavelengths of light corresponding to the energy differences between allowed orbits.
What type of spectrum do atoms produce when emitting or absorbing light?
The light emitted or absorbed by an atom produces a discrete spectrum, consisting of a set of distinct lines.
Are the wavelengths emitted by an atom the same as those it absorbs?
Yes, the wavelengths that an atom emits are the same as the wavelengths it absorbs.
How does the discrete spectrum of atomic light compare to thermal radiation?
The discrete spectrum of atomic light has distinct lines, while thermal radiation produces a continuous spectrum with light at all wavelengths.
Do different atoms have the same sets of energy levels?
No, different atoms (elements) have different sets of energy levels.
What is the significance of the unique energy levels of different elements?
Each element has a different set of spectral lines, which allows for its identification.
How can an element be identified?
Each element can be identified by its unique spectrum.
When do we observe an absorption spectrum What does the spectrum look like?
When a cloud of cooler gas is directly between the observer (prism) and a hot black body. Most colors with missing lines.
When do we observe an emission spectrum? What does the spectrum look like?
When a cloud of cooler gas is at an angle (not directly in line) between the observer (prism) and a hot black body. Basically no colors besides a few lines on spectrum
When do we observe a continuous spectrum? What does the spectrum look like?
When there is nothing between the observer (prism) and the hot black body. All colors on spectrum
What happens to the wavelength when a source of light or sound is moving away from you?
The wavelength, as seen by you, becomes longer.
What happens to the wavelength when a source of light or sound is moving toward you?
The wavelength, as seen by you, becomes shorter.
What are the two types of optical telescopes?
Reflecting and refracting telescopes.
Which type of telescope do modern astronomers use and why?
Modern telescopes are all reflectors because:
- Lenses are heavy and can only be supported at the edges.
- Lenses absorb more light than mirrors.
- Light is refracted differently depending on wavelength, causing chromatic aberration.
- Lenses need two optically acceptable surfaces, whereas mirrors only need one
What is chromatic aberration?
Chromatic aberration occurs when light traveling through a lens is refracted differently depending on wavelength.
Why is a larger telescope better at separating two nearby objects in the sky?
A larger telescope has better resolving power, making it easier to separate two objects that are nearly in the same direction.
What is resolving power?
Resolving power is the smallest angle that can be seen with a given telescope.
Do larger telescopes have better resolving power than smaller ones?
Yes, large telescopes have greater resolving power than small ones.
What limits the resolving power of all earthbound optical telescopes?
The resolving power of earthbound optical telescopes is limited by the turbulence of the air.
What is Angular Resolution?
Angular resolution is a measure of a telescope’s ability to distinguish between two closely spaced objects in the sky. It refers to the smallest angle between two objects that a telescope can resolve, meaning they can still be seen as separate entities rather than a single blurred object. Smaller angular resolution values indicate better resolving power.
What limits the resolving power of ground-based optical telescopes?
The resolving power of all ground-based optical telescopes is limited by the blurring effect of turbulence in the Earth’s atmosphere, which distorts the light passing through it. This phenomenon reduces the telescope’s ability to distinguish fine details.
The atmosphere limits how clearly we can see from Earth. Ways to solve this problem:
- Place telescopes on mountains to minimize atmospheric distortion.
- Use adaptive optics to correct for atmospheric turbulence.
- Put telescopes in space to avoid atmospheric interference altogether.
Which types of light can be observed from the ground, and which must be observed from space?
Optical and radio waves can be observed from the ground.
Light at other wavelengths (such as infrared, ultraviolet, X-rays, and gamma rays) must be observed from space due to the atmosphere’s opacity.
What are the key features of radio telescopes?
Similar in design to optical reflecting telescopes.
The reflecting surface needs to be smooth on the scale of the wavelengths observed (radio waves are longer).
The surface is less sensitive to imperfections and can be made very large.
Example: Green Bank Telescope.
What is radio interferometry?
Combines information from several widely spread radio telescopes as if it came from a single dish.
The resolution will be equivalent to that of a dish with a diameter equal to the largest separation between dishes, known as the baseline.
Why must infrared telescopes be very cold?
Everything emits radiation based on its temperature.
Cold objects emit in the infrared; therefore, to observe in the infrared, the telescope must be extremely cold (e.g., cooled to 4 K by liquid helium) to ensure it does not emit more radiation than the objects being observed.
This is essential to keep the thermal background low and minimize interference.
GALEX: Galaxy Evolution Explorer, what type of telescope is it?
Space-based
UV telescope
How do we observe X-rays and gamma rays?
X-rays and gamma rays cannot reflect off mirrors like longer wavelengths (e.g., optical or radio waves).
New techniques are required to focus these shorter wavelengths.
X-rays can be focused by reflecting them at a very shallow angle.
Specialized instruments, such as X-ray telescopes, utilize this principle to observe these high-energy wavelengths.
How do we focus on gamma rays?
Gamma rays can’t be focused. We just put a detector in space and wait for them
How long does it take for the Moon to orbit the Earth, and what determines its phases?
The Moon orbits the Earth every 29 days.
Its phase is determined by its position in its orbit around the Earth.
How does the Moon’s rising time and visibility change throughout its phases?
The Moon rises about an hour later every day. The visible fraction of the Moon’s disk corresponds to the fraction of the night it is up:
Waxing Phase: Visible in the first part of the night.
Waning Phase: Visible in the last part of the night.
Full Moon: Entire disk is visible and up for the entire night.
New Moon: Disk is not visible and up for none of the night
Please Fill out the moon phase, rise time, time highest, and set time chart.
Do it bozo
What is a lunar eclipse and when does it occur?
A lunar eclipse occurs when Earth’s shadow falls on the Moon.
It can only happen when the Sun and Moon are on opposite sides of the Earth; thus, the Moon must be in its full phase.
A lunar eclipse is visible simultaneously from everywhere on the night side of Earth.
What happens during a solar eclipse?
Shadow of the Moon falls on Earth
Can only happen when Moon is between the Earth and the Sun: Moon must be new, You can see an eclipse of the Sun only if you are on
the path of the Moon’s
shadow
What are eclipse seasons and how often do they occur?
Eclipse seasons occur about once every 6 months. During these seasons, the line from the Sun to Earth aligns with the plane of the Moon’s orbit. Eclipses of the Moon and Sun can occur during these periods.
What is the Celestial Sphere?
The Celestial Sphere is an imaginary sphere that represents the sky, centered around the Earth.
In what direction does the Celestial Sphere appear to rotate?
The Celestial Sphere appears to rotate once a day from east to west.
Why does the Celestial Sphere appear to rotate?
The apparent rotation of the Celestial Sphere is due to the Earth’s actual rotation from west to east.
How does the Earth’s rotation appear from the North Pole?
From the North Pole, the Earth’s rotation appears counterclockwise.
What is Polaris commonly known as?
The North Star.
How do stars, the Sun, the Moon, and planets appear to move from the northern hemisphere?
They appear to move from east to west in a circle around Polaris, the North Star.
Where is Polaris located in relation to the North Pole?
Polaris is directly overhead at the North Pole.
Where is Polaris located when you are at the equator?
Polaris is on the horizon at the equator.
What does the altitude of Polaris indicate?
The altitude of Polaris is equal to your latitude.
Why is Polaris important in celestial navigation?
It serves as a key reference point for determining latitude.
What are lines of latitude?
Lines of latitude are parallel to the equator.
What do lines of longitude do?
Lines of longitude connect the North and South poles.
How do lines of latitude and longitude help in navigation?
They provide a grid system for identifying precise locations on Earth’s surface.
Where is the Sun positioned during the winter solstice?
The Sun is over a point 23.5° south of the equator.
What occurs on the summer solstice concerning the Earth’s axis?
The axis is tilted toward the Sun.
Where is the Sun located during the summer solstice?
The Sun is directly over a point 23.5° north of the equator.
Where is the Sun positioned during the Vernal Equinox (spring)?
The Sun is directly above the equator.
Where is the Sun located during the Autumnal Equinox (fall)?
The Sun is directly above the equator.
What are the two points where the ecliptic intersects the celestial equator?
The Vernal Equinox (spring) and the Autumnal Equinox (fall).
Why does sunlight appear more direct in the summer?
Because the northern hemisphere is tilted toward the Sun.
What happens to the northern hemisphere during winter?
It is tilted away from the Sun.
How do seasons occur in the southern hemisphere compared to the northern hemisphere?
The seasons occur at opposite times; when it’s summer in the northern hemisphere, it’s winter in the southern hemisphere, and vice versa.
What is precession?
Precession is the change in the orientation of the rotational axis of a rotating body.
How long is the cycle for the direction of Earth’s rotational axis to change?
The cycle lasts approximately 26,000 years.
How long is the period for Earth’s axis of rotation to precess?
Earth’s axis of rotation precesses with a period of 26,000 years.
What celestial event will occur in about 12,000 years related to the North Star?
In about 12,000 years, Vega will become the North Star instead of Polaris.
When will Polaris again be the North Star?
Polaris will again be the North Star in 26,000 years when Earth’s axis points in its current direction.
How did ancient astronomers and philosophers perceive the celestial sphere?
They took the idea of the celestial sphere literally, believing it to be a physical structure.
What was Aristotle’s belief regarding the structure of the sky?
Aristotle believed the sky was composed of about 50 concentric, crystalline spheres with celestial objects attached to them, with Earth at the center.
What is the term for the model of the solar system proposed by Aristotle?
The geocentric model of the solar system.
What is retrograde motion in terms of planetary movement?
Retrograde motion is when the path of a planet relative to the background stars appears to loop or zigzag, occasionally reversing direction in the sky.
What causes the appearance of retrograde motion in planets?
Retrograde motion occurs due to the relative positions and motions of the Earth and other planets in their orbits around the Sun.
What is the Ptolemaic model of the solar system?
The Ptolemaic model is a geocentric model in which each planet moves on a small circle called an epicycle, while the center of the epicycle moves around the Earth in a larger circle called the deferent.
What are epicycles in the Ptolemaic model?
Epicycles are small circles on which each planet moves, contributing to the overall motion observed in the sky.
What is the deferent in the Ptolemaic model?
The deferent is the larger circle around which the center of the epicycle moves, creating the overall motion of the planet.
How does the Ptolemaic model explain the retrograde motion of planets?
In this model, a planet moves backwards (retrograde motion) when it is at the part of the epicycle closest to the Earth, despite its overall west-to-east motion.
Who was Nicolaus Copernicus?
icolaus Copernicus (1473 – 1543) was an astronomer who proposed a heliocentric model of the solar system, suggesting that the Earth rotates about a fixed axis and revolves around the Sun.
What did Copernicus explain about the rotation of the celestial sphere?
Copernicus explained the rotation of the celestial sphere by assuming that the Earth rotates about a fixed axis while the celestial sphere remains stationary.
How did Copernicus account for the apparent motion of the Sun?
He accounted for the apparent motion of the Sun, which seems to move once around the celestial sphere per year, by proposing that the Earth revolves yearly around the Sun.
What is the heliocentric model?
The heliocentric model places the Sun at the center of the solar system, with other planets, including Earth, moving around it in perfect circles.
How did Copernicus adjust the speeds of the planets in his model?
He adjusted the speeds of the orbits based on their distance from the Sun, with closer planets moving faster.
What is the order of the planets in the Copernican model?
The order of the planets is Mercury, Venus, Earth, Mars, Jupiter, and Saturn.
How does Earth’s speed compare to other planets according to Copernicus?
Earth, being the third planet from the Sun, moves faster than Mars, Jupiter, and Saturn, but slower than Mercury and Venus.
Who was Tycho Brahe?
Tycho Brahe (1546–1601) was a Danish astronomer known for his accurate astronomical observations before the invention of the telescope.
What significant astronomical event did Tycho Brahe observe in 1572?
In 1572, Tycho Brahe observed a new star, which was actually the death of an old star, known as a supernova.
What tools did Tycho Brahe use for his observations?
Tycho Brahe used specially designed instruments to measure the precise positions of stars and planets, as telescopes had not yet been invented.
What was the primary focus of Tycho Brahe’s work?
Tycho Brahe focused on making years of careful observations of the positions of planets against the background stars.
Who was Johannes Kepler?
Johannes Kepler (1571–1630) was a German mathematician, astronomer, and astrologer known for his laws of planetary motion.
How did Kepler come to work with Tycho Brahe?
Kepler was recognized as a brilliant mathematician by Tycho Brahe, who invited him to help analyze his extensive astronomical data.
What significant discovery did Kepler make regarding planetary motion?
Kepler discovered that the observed paths of the planets followed from three simple laws, derived from Tycho’s data.
How long did it take Kepler to formulate his laws of planetary motion after meeting Brahe?
It took over fifteen years from the time Kepler met Brahe to formulate his laws of planetary motion.
What is Kepler’s First Law of Planetary Motion?
Planets move in ellipses with the Sun at one focus.
What is Kepler’s Second Law of Planetary Motion?
The line from the Sun to a planet sweeps out equal areas in equal times, meaning planets move faster when closer to the Sun and slower when farther away.
What is Kepler’s Third Law of Planetary Motion?
The period of each planet is related to its average distance from the Sun by the formula P^2 = a^2, where 𝑎 is the average distance from the Sun in AU and P is the period in years.
Who built the first telescope?
The first telescope was built by the Dutch spectacle maker Hans Lippershey in 1608.
What did Galileo do with telescopes?
Galileo constructed his own, more accurate version of the telescope and became the first person to make significant astronomical observations with it.
What significant discovery did Galileo make regarding Jupiter?
Galileo discovered the moons of Jupiter.
What features did Galileo observe on the Moon?
Galileo observed craters on the Moon.
What astronomical feature did Galileo resolve into individual stars?
Galileo resolved the Milky Way into individual stars.
What did Galileo observe that provided evidence for the Copernican model?
Galileo observed the phases of Venus, which allowed a test of the Ptolemaic and Copernican models, agreeing with Copernican predictions.
What did Galileo’s experiments demonstrate about the speed of falling objects?
Galileo’s experiments showed that the speed of fall increases uniformly with time, demonstrating the law of uniform acceleration.
What was Galileo’s realization about the effect of force on motion?
Galileo realized that the effect of force is not to produce motion but to change motion, specifically to produce acceleration.
What happens to a body when no force acts upon it, according to Galileo?
A body on which no force acts moves at a uniform speed.
What are some of the major contributions of Isaac Newton?
Isaac Newton established the laws of classical mechanics, invented the reflecting telescope, and developed calculus.
What does Newton’s Second Law of Motion state?
The acceleration of an object is directly proportional to the force applied and inversely proportional to the object’s mass.
What is the formula for Newton’s Second Law of Motion?
The formula is F = ma, where F is force, m is mass, and a is acceleration.
How does mass affect acceleration according to Newton’s Second Law?
The same force will make an object with a small mass accelerate more than an object with a larger mass.
What does Newton’s Third Law state?
For every action, there is an equal and opposite reaction. This means that when two bodies collide, they exert equal and opposite forces on each other.
What happens when a low mass asteroid collides with a high mass planet according to Newton’s Third Law?
The low mass asteroid and the high mass planet exert equal and opposite forces on each other when they collide.
How does the mass of the asteroid affect its acceleration during a collision with a planet according to Newton’s Second Law?
According to Newton’s Second Law (F = ma), in response to the force, the low mass asteroid accelerates more than the high mass planet.
In Newtons law of gravity what does each variable represent?
F = (GMm/r^2)
F: gravitational force between the two objects
G: Newton’s constant of gravitation
M: mass of object 1
m: mass of object 2
r: distance between the centers of the objects
What are the effects of increasing the distance 𝑟 on the gravitational force 𝐹?
As the distance 𝑟 increases, the gravitational force 𝐹 decreases, following an inverse square relationship.
