Ch: 22 What is light?
What is the speed of light in the near vacuum of space?
300,000,000 m/s
How is light different from other kinds of waves?
A light wave does not have to travel through matter
What is light?
A type of energy that travels as a wave
How long does light take to travel from the sun to Earth?
About 8.3 minutes
Describe how an Em wave is produced.
An EM wave can be produced by the vibration of an electronically charged particle. When a particle vibrates, or moves back and forth, the electric field around it vibrates. When the electric field starts vibrating, a vibrating magnetic field is created. Together they produce an EM wave.
Why do you see lightning before you here thunder?
Because light waves travels faster than sound waves
The major source of energy on Earth are __________ from the sun.
EM waves
Every object is surrounded my an ____________________.
Electric field
A wave that consists of changing electric and magnetic fields and that can travel through empty space is a(n) __________.
Electromagnetic wave
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.
Why does only a small part of the total energy given off by the sun reach Earth?
Most of the sun gives off energy as EM waves in all different directions and go into 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.
From where does the energy carried by an EM wave come?
When a particle vibrates, or moves back and forth, the electric field around it vibrates. When the electric field starts vibrating, a vibrating magnetic field is created. Together they produce an EM wave.
AN electric field pulls __________ objects toward it and repels ________________ objects to it.
oppositely, like-charged
The electric and magnetic fields on 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
Name two things that produce light.
sun, and light
