Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key


Play button


Play button




Click to flip

17 Cards in this Set

  • Front
  • Back
What is a form of energy?
Our primary source of light is _______.
How does light energy changed to heat energy?
Light energy from the sun travels through space, strikes the earth and is changed to heat energy which warms the air.
What would happen without heat energy?
The earth would quickly become too cold for life.
Where else can light energy be stored?
in green plants
What happened when the plants died millions of years ago?
They were buried by sediment and came coal, natural gas and oil. Today we burn these fuels for energy.
Name ways light can be produced.
1. Hot materials glow
2. the light from fire is
due to the hot gases in
the flame.
3. the sun and stars are
masses of intensly, hot
4. the light from an
electric light bulb
comes from tiny, hot,
glowing wire.
How does light travel?
in straight lines. Because light travels in a straight line, we can't see around corners and objects in the path of light beam cast shadows.
What happens when light strikes an object?
it is reflected, absorded or it passes through.
What happens when light strikes a highly reflective surface such as a mirror?
It bounces off in a straight line at the same angle that it hit the mirror.
How can you describe on object?
It can be transparent, translucent or opaque.
What are transparent materials?
they allow light to pass through easily.
What are translucent materials?
they allow some light to pass through and scatters the rest.
What are opaque materials?
they block or absorb all light.
How many miles per second does light travel?
186,000 miles per second (enormous speeds?
What happens when light passes through transparent substances such as glass, air or water?
it slows down. Its path changes so that light rays are bent as they pass through.
What is refraction?
The sudden change in direction of a light beam.