Light Flashcards
What are objects that produce light called?
Luminous
What are non-luminous objects?
Objects that we see because light from luminous sources reflects off them and into our eyes.
What are transparent materials?
Materials through which light easily travels
What are opaque materials?
Materials through which light cannot travel.
What is the light ray striking a mirror called?
The incident ray
What is the light ray travelling away from the mirror called?
The reflected ray.
With what are the angles of incidence and reflection measured?
The normal
What is the Law of Reflection?
The angle of incidence is always equal to the angle of reflection.
Experiment to prove the law of reflection [10]
- Draw a straight line AOB on a sheet of white paper.
- Using a protractor, draw a normal at O.
- Using the protractor, draw straight lines at angles between 15 and 75 degrees to the normal.
- Rest a plane mirror on the line AOB.
- Using a ray box, shine a ray of light along the 15 degree line.
- Mark two crosses on the paper along the reflected ray.
- Remove the mirror and use a ruler to draw a line joining the crosses and to point O. This is the reflected ray.
- Using a protractor, measure the angle of reflection.
- Record in a table the angles of incidence and reflection.
- Repeat for various angles between 15 and 75 degrees.
What is the image in a plane mirror?
Virtual, the same size as the object, laterally inverted and the same distance behind the mirror as the object is in front.
What is refraction?
The change of direction of a beam of light as it travels from one material into another.
Why does refraction occur?
Because light travels at different speeds in different materials.
Is the speed of light in water lower or higher than the speed of light in air?
Lower
When refraction occurs, what always happens to some of the light?
Some of the light is always reflected internally.
When light slows down, what happens?
It bends towards the normal.