Light Flashcards
What is light?
A form of energy.
What are luminous objects?
Give an example of something that is and isn’t luminous.
Produces its own light,
The son is luminous, but the moon isn’t, as it reflects the sun’s light and doesn’t produce its own.
What do the following terms mean:
Opaque?
Translucent?
Transparent?
Light cannot pass
Some light can pass
Light can pass
What is a ray?
A straight line which light moves in.
What is a beam?
Two or more rays of light together.
What are the 3 types of beam?
Parallel beam (rays parallel)
Convergent beam (rays point inwards)
Divergent beam (rays point outwards)
What is the speed of light?
300,000,000m/s or 3 x 10^8m/s
What are shadows?
What can they tell us about light.
Formed when light strikes an opaque object. Light cannot pass through or go around, forming an area with little to no light in it.
Tells us that light travels in a straight line.
What is regular reflection?
Light strikes a smooth surface and all rays are reflected in the same direction.
What is diffuse reflection?
When light hits a ‘rough’ object and is reflected in all directions.
What is lateral inversion in a mirror?
When an object is reflected in a mirror, left is right and right is left on the image.
What is refraction?
When light changes it’s speed and direction when it passes from one material to another.
What is the relationship between the angle of incidence and the angle of reflection in a mirror?
They are equal.
What is a virtual image?
Cannot be formed on a screen, e.g. mirrors.
What is the relationship between the distance between the object and the mirror and the distance between the mirror and the image behind it?
They are equal.
What is the relationship between the angle of incidence and the angle of refraction?
Angle of refraction is less than angel of incidence.
Is light refracted towards or away from the normal when it travels from a less to more dense material?
Towards the normal.
Is light refracted towards or away from the normal when it travels from a more to less dense material?
Away from the normal.
What is the relationship between the direction of the incident ray and the emergent ray in a glass block?
They are parallel.
What happens to the speed of light when it enters a glass block?
Decreases
What happens to the speed of light when it leaves a glass block?
Increases
What does a wavefront diagram look like?
How does it interact with a glass block.
Light represented as a series of parallel lines (wavefronts) lined up.
When it reaches a glass block, one end of the wavefront enters the glass block before the other. As this end slows down more, it causes the wavefront to change direction. When the beam leaves the glass block, the other end leaves before the first, causing it to change back again.
What is internal reflection?
When light passes from glass into air, there is a refracted ray into the air and a reflected ray back into the glass.
What is the critical angle?
As the angle of incidence increases, the angle of refraction also increases until a certain angle of incidence called the critical angle, represented as c, is reached. This makes the angle of refraction 90, and it fails to emerge into the air.
In angles of incidence above c the refracted ray disappears and all light is reflected inside the glass. This is called Total internal reflection. Emphasis on total.
