Section 1: What is Light?
How long does light take to travel from the sun to the Earth?
8.3 min
What is light
A type of energy.
Where does the energy carried by an EM wave come from?
An EM wave carries energy released by the original vibration of a particle.
How is an EM wave produced?
An EM wave is produced by the vibration of an electrically charged particle. When the particle vibrates, the electric field around it also vibrates. When the electric field starts vibrating, a vibrating magnetic field is created.
A major source of energy from the sun on Earth are __.
EM waves
Where do fields exist and what do they do?
Fields exist around certain objects and can exert a force on another object without touching that object.
What if the speed of light in the near vacuum of space?
In the near vacuum of space, the speed of light is 300,000,000 m/s (or 300,000 km/s)
How is light different from other kinds of waves?
Light does not require matter through which to travel. Other kinds of waves must travel through matter.
Why do you see lighting before you hear the thunder that accompanies it?
Lightning is seen before thunder is heard because light travels much faster than sound.
Why does only a small part of total energy given off by the sun?
Most of the energy travels away in space.
Describe two ways in which the sun's energy is used on Earth.
Plants use photosynthesis to store energy from the sun. Animals use and store energy by eating plants or eating other animals that eat plants. Fossil fuels store energy from the sun.
Name two things that produce light.
The sun and light bulbs produce light.
Every charged object is surrounded by an __________
electric field
A wave consists of changing electric and magnetic fields and that can travel through empty space is a_____.
electromagnetic wave
Every magnet is surrounded by a ____________
magnetic field
An electric field pulls _________ objects toward it and repels ________ objects.
oppositely-charged, like-charged
The electric and magnetic fields of an electromagnetic wave are ___________ to each other and to the direction of the wave's motion.
perpendicular
The transfer of energy as electromagnetic waves is called_____
radiation
Calculate how long light takes to travel from Earth to the moon if the distance between them is 384,000 km.
time 384,000 km/300,000 km/s; time 1.28 s
