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What are the two major motions of Earth as it travels through space?
Earth rotates on its axis and revolves around the Sun.
Solstices occur twice a year (around June 20–21 and December 21–22); summer solstice = longest day, winter solstice = shortest day.
Why don’t solar and lunar eclipses occur every month?
How long does it take Earth to rotate once and how long to orbit the Sun once?
Earth rotates in about 24 hours and revolves around the Sun in about 365¼ days.
State one similarity and one difference between light waves and mechanical waves.
Similarity: both transfer energy and have wavelength, frequency, amplitude; Difference: mechanical waves need a medium, light does not.
Which motion causes day and night on Earth?
Earth’s rotation causes day and night.
What are equinoxes and what is special about daylight on those days?
Equinoxes occur around March 20 and September 22; day and night are about equal (about 12 hours each).
Describe how the Moon’s phases happen in terms of positions of the Sun, Earth, and Moon.
As the Moon orbits Earth, different portions of its sunlit side are visible from Earth, producing phases (new, crescent, quarter, gibbous, full).
Give a short definition of an eclipse.
An eclipse happens when one object moves into the shadow of another object in the solar system.
Why do higher-frequency waves transfer more energy than lower-frequency waves?
Higher frequency means more energy delivered per second (more wave cycles per unit time).
What causes the seasons on Earth?
Seasons are caused by Earth’s axial tilt of about 23.5∘23.5∘ as it revolves around the Sun.
Name three everyday uses of satellites.
GPS/navigation, communications (phone/TV/data), weather and Earth observation.
What causes tides and when do spring tides occur?
Tides are mainly caused by the Moon’s gravity (and the Sun’s gravity); spring tides occur at new and full moon when Sun, Moon, Earth are aligned.
Define “orbit” in one sentence.
To orbit is to move around another object in a complete path (like a circle or oval) due to gravity.
How can the structure of a bluebird’s feathers make them look blue (use wave ideas)?
Microstructures in feathers scatter light so shorter (blue) wavelengths are reflected more, making the feathers look blue.
Explain what would happen to seasons and daylight hours if Earth had no tilt on its axis.
Without tilt, Earth would have little or no seasonal change and roughly equal daylight hours year-round.
What two factors determine the force of gravity between two objects?
Mass and distance; greater mass increases gravitational force and shorter distance increases force.
When do neap tides occur and why are tidal ranges smaller then?
Neap tides occur at first and third quarter moons when Sun and Moon are at right angles relative to Earth, partially canceling tidal forces and producing smaller tidal ranges.
What is the Moon cycle (another name for the changing appearance of the Moon)?
The Moon cycle is the changing appearance of the Moon as it orbits Earth (its phases).
What is amplitude in terms of waves?
Amplitude measures a wave’s maximum displacement from its rest position.
Define inertia
Inertia is the tendency of an object to resist changes in its motion.
Why do black objects appear black?
Black objects absorb most visible light and reflect little, so little light reaches our eyes; this is why our eyes perceive black.
Explain how the Moon’s low surface gravity and lack of atmosphere lead to large temperature ranges.
Low gravity cannot hold a thick atmosphere; without an atmosphere heat isn’t spread or retained, so large temperature swings occur between lunar day and night.
Explain why radiation is the main form of heat transfer in space.
Space is nearly a vacuum so there’s no medium for conduction or convection; hence radiation (electromagnetic waves) transfers heat.
Explain the primary difference between an analog signal and a digital signal.
Analog signals vary continuously over time; digital signals represent information with discrete steps (bits).