3.3 Refraction Flashcards
What happens if the angle of incidence is 0degrees?
the wave experiences a change in speed but not a change in direction.
What is refraction?
The bending of a wave (changes direction) when a wave traverses a boundary between two mediums at an angle.
What happens when an incident ray passes from air to glass (less dense to more dense) ?
The ray bends towards the medium.
i>r
What happens when an incident ray passes from glass to air (more dense to less dense) ?
ray bends away from the normal
i<r
What is a lens?
An object designed to refract light rays for a given purpose.
What effect does a converging lens have on parallel rays?
Reflects them to a focus
What is focal length? What is the symbol and unit?
Distance between the centre of the lens and focal point
f
metres (m)
How does changing the curvature effect the focal length of a converging lens?
higher curvature means shorter focal length
lower curvature means longer focal length
What effect does a diverging lens have on parallel rays?
reflects the rays away from a focus.
How does changing the curvature effect the divergence of a diverging lens?
lower curvature means lower divergence
higher curvature means higher divergence
What three things are ray diagrams used to illustrate and determine?
- location
- orientation
- magnitude
What two ways can an image be classified in terms of location?
real- can be formed on a screen (opposite side of lens to the object)
virtual- cannot be formed on a screen (same side of lens as object)
What two ways can an image be classified in terms of orientation?
upright-same as object
inverted-opposite to object
What two ways can an image be classified in terms of magnitude?
enlarged- larger than object
diminished- smaller than object
Where do the two lines go in a ray diagram when looking at images?
- first line goes from top of object to lens in a straight line and then a straight line form that point of lens through the first focal length
- second line goes from top of object through origin
Where is an image formed on a ray diagram?
Where the two lines meet.
What does the power of a lens give?
A measure of the degree of refraction the lens produces
Which equation links power and focal length?
P=1/f
f=1/P
What is power measured in? (lenses)
dioptre D
Which lens have a positive power and which have a negative power?
- converging positive (+)
- diverging negative (-)
What is long sight?
When long distance is clear but close is fuzzy
image is past retina
What is short sight?
close objects are clear but distant objects are fuzzy
image doesn’t reach retina
Which lens fixes short sight? How?
Diverging lens diverges rays so image is formed further back-on the retina
Which type of lens fixes long sight? How?
Converging lens brings rays to a point further forward -on the retina
