Light Flashcards
Which colour of light has the least and most refraction in order of wave length
Red = least
Violet = most
Rainbow in between
When white light is shone through prism what is produced
A spectrum
Why are spectrums produced
As different colours travel at different speeds in glass
What is important about reflection of light?
Angle of incidence = angle of reflection
What are 2 types of reflection
Regular and diffuse
What can u say about an image
It’s virtual
It’s the same size as the object
It’s laterally inverted
It’s the same distance behind the mirror as the object is in front
What is a virtual image
a virtual image is the collection of focus points made by extensions of diverging rays
What can u say about refraction of light going from air to glass and water
It slows in glass and water going from air
What happens when light slows
It bends towards the normal
What happens when light speeds up
It bends towards the normal
What conclusion do u get about the relationship between the angle of incidence and the angle of reflection
This tells us that i is not directly proportional to r (because the graph is not a straight line), but that i and r have a positive correlation (as i increases, r increases).
What conditions are there for TIR To occur in a semi-circular glass block
Angle of incidence is increased passed the refracted ray angle
When does TIR occur
When the angle of incidence in the glass is greater than the critical angle
In terms of TIR how do optical fibres enable long distance communication
So long as the fibre isn’t bent too tightly light will strike the boundary at an angle greater than the critical angle and be totally internally reflected at the surface
What does a converging lens do
It converges rays parallel to the central axis to the same point on the opposite side of the lens
This point is called the principal focus
What does a diverging lens do
It diverges Rays parallel to the principal axis so that they appear to be diverging from the same point after refraction in the lens
This point is called the principal focus
Define the focal length of a converging lens
The focal length is from the centre of the lens to the principal focus in front of the lens
Define the focal length of a diverging lens
The focal length is from the centre of the lens to the principal focus behind the lens
Where are the 2 main focii for lenses
On either side of the lens
Describe an experiment that uses a distant object to measure the focal length of a converging lens
Tape a ruler to a table
Place a white screen in a holder at the zero mark then place the convex lens in a holder as close as possible to the screen
Slowly move the lens away from the screen until the inverted image of a distant image eg a tree is as clear as possible
Record the number at which the lens is at. This is the focal length
Repeat these steps 3 more times and get an avg value for the focal length of the lens
Can real images be focused onto a screen
Yes
Can virtual images be focused onto a screen
No
What is the principal of a simple camera
Camera gives a diminished real image
What is the principal of a projecter
Projector gives a magnified real image
What happens When the angle of incidence in the glass reaches the critical angle
the angle of refraction in the air becomes 90 degrees
How does short sightedness usually occur
When the eye grows slightly too long so that light doesn’t focus on the retina properly
Where do the light rays focus for a short sighted person
Just in front of the retina, resulting in distant objects appearing blurred
How does long sightedness usually occur
When the eyeball is too short or the lens can’t be made thick enough to focus the light rays on the retina
Where do the light rays focus for a long sighted person
They focus behind the retina so nearby objects appear blurred
What lens corrects short sightedness
Concave (diverging)
What lens corrects short sightedness
Convex (converging)
