P5.3 Flashcards
Ray diagram
A diagram that uses rays to model what happens to beams of light
3 things to keep in mind when drawing a ray diagram
- draw lines to represent rays
- draw ‘normal’ line @ 90 degrees to the surface
- measure the angles from the normal line to the ray
Why are electromagnetic waves refracted?
- light goes from air to another denser medium (e.g. glass)
- it slows down and bends TOWARDS the normal line
(If difference in density i salarier, change in direction is aslo larger)
Why are radio waves/sound waves refracted
- they are sent up
- they reflect off a layer in the atmosphere called the ‘IONOSPHERE’
- they go back down at the same angle as before
- hence used for satellite communication
If a ray speeds up, which way does it bend
It bends away from the normal line, hence a larger angle of inflection
Meaning of ‘emit’
To give out
Meaning of ‘transmit’
To let through
Convex lens (fat or inflated) - can be said as ‘converging’
Refracts ray to a principle focus,focal point. Brings them all inwards towards to normal line
Concave lens (thin, diverging)
Spreads out the light, sends the rays away from the normal line
Focal length
Distance from the centre of a lens to the principle focus / focal point
(Look at page 162 figure 2 if confused)
To fix long sightedness - when light focuses to far behind the retina
CONVEX (fat) lens
To fix short sightedness - when light focuses to in front of the retina
CONCAVE (thin) lens
Example of convex lenses
- magnifying glass
- telescope
- microscope
Examples of concave lenses
- spy holes in door
- back windows of coaches
Dispersion
The seep reaction of colours in white light into a continous spectrum
