convex lenses/ concave lens Flashcards
What happens when a wave moves from a less dense object to a more dense object
wave bends towards the normal and the velocity of the wave slows
What happens when a wave moves from a more dense object to a less dense object
The wave bends away from the normal, and the velocity increases
describe the shape of a convex lens
thicker at the centre than at the edges
what is the symbol for the convex lens
<——>
how do convex lens form an image
parallel rays of light are brought to a focus at the principal focus
what is the focal length
The distance from the centre of the lens to the principal focus
what image is always produces by a concave lens
virtual
what are the properties of the image if the object is more than 2 focal lengths from the lens
- image is diminished
-image is inverted - image is real
what are the properties of the image if the object is between 1 and 2 focal lengths from the lens
- image is magnified
-image is inverted
-image is real
how to draw ray diagram for magnifying glasses
- Start by drawing a ray of light from the top of the object through the centre of the lens
- Draw another ray from the top of the object running parallel with the principal axis
- Ray passes through principal focus, but the rays do not meet at a point
- so extend the rays behind the lens with a dotted line ( where the dotted lines meet shows the position of the image )
how do you know in a ray diagram is the image is real of virtual
Real: the rays actually meet at a point
virtual : they don’t actually meet at a point they just appear to meet
what is the only time when a convex lens produces a virtual image
when it is used as a magnifying glass
What is the equation for magnification
image height / object height
why does magnification not have a unit
- It is the ratio between image height and object height
- Ratios don’t require units
what is the symbol for concave lens
> ——–<
describe the shape of a concave lens
thicker at the edges than the centre
how does a concave lens form an image
- A concave lens makes the light rays spread out ( the light rays diverge )
What properties will a concave lens image alwyas have
- image will always be diminished
- the right way up
- virtual
how does the angle of reflection and angle of incidence appear during reflection
the same ( angle of reflection = angle of incidence )
what is specular reflection
reflection that takes place on smooth surfaces
- produces an image
what is diffuse reflection
- doesn’t produce an image
- Light rays are scattered from a rough surface
what is white light
a mixture of all the different colours
how do colour filters work
- absorbing specific wavelengths and transmitting other wavelengths
what is the colour of an opaque object determined by
which wavelengths of light are more strongly reflected
