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
the central ray passes through the lens without being refracted because the ray is passing directly along the normal
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
what colour does the object appear if all wavelength are reflected equally
white
what colour does the object appear if all wavelength are absorbed
black
what determines the colour of visible light waves
the wavelength and frequency of the light waves
why to white objects appear white
because they reflect all of the wavelengths of visible light equally
why do black objects appear black
because they absorb all the wavelengths of visible light
what colour of visible light has the highest frequency
blue
what colour of visible light has the largest wavelength
red
