2.2 Light Flashcards
When light is reflected by a plane mirror how are the angles of incidence and reflection measured ?
Angles of incidence and reflection are measured from a line at right angles to the mirror known as the normal
How are angles of incidence and reflection measured
From the normal
What is the normal ?
The normal is a line 90 degrees to the material
What is the angle of incidence equal to ?
The angle of incidence is equal to the angle of reflection
What is the incident ray ?
The ray going into the material
What is the reflected ray ?
The ray reflected from glass
What is the law of reflection ?
The angle of incidence equals the angle of reflection
What are the properties of an image in a plane mirror ?
- same height
- same distance away
- Inverted laterally
- upright
What is a refraction ?
Refraction is the change of direction of a beam of light as it passes from one medium to another. The bending of light as it changes speed.
What way does light bend and how can you remember this ?
Fast
Away
Slow
Towards
When does a ray stay the same and not bend when entering the block?
A ray parallel to the normal doesn’t bend as it enters the block
What happens the greater the refraction in regards to speed of light?
The greater the refraction, the larger the change of speed of light
What is dispersion ?
The splitting up of white light into the seven different colours
What happens as the light passes through the glass prism ?
The different colours move at different speeds causing the white light to split up (disperse)
What colour is refracted the least and how does this relate to the change of speed ?
Red is refracted the least so it is slowed the least, and is therefore the fastest
What are the two types of lenses ?
- Converging (convex)
- Diverging (concave)
What happens to light as it passes through a convex lens ?
It will cause the light to converge to a focal point
What happens to light as it passes through a concave lens ?
The concave lens will diverge the light
What is the focal length ?
The distance from the centre of a lens to the principal focus
What are the steps for a ray diagram for a camera ?
- Take light and pass it through a lens with a small focal value
- The light meets on a film
- The light burns the film producing an image
- The image is diminished, inverted and real
What are ray diagrams used to show ?
They are used to show where an image of an object will be and there are 3 main rays drawn on these diagrams
Where do the main 3 rays pass through and are drawn on ray diagrams ?
1) Ray 1 is refracted through the principal focus of the lens because it is parallel to the lens axis before the lens .
- This is drawn through the lens at a right angle through F
2) Ray 2 passes through the centre of the lens without change of direction, this is because the lens surfaces are parallel to each other at the axis.
- Drawn through the middle
3) Ray 3 passes through the principal focus of the lens, before the lens so it is refracted by the lens parallel to the axis.
- Drawn through F then passing through the lens at a right angle
What image is created by a projector ?
- An inverted object (projector)
- Light passes through the lens and creates an image beyond 2F
- The image is upright, larger/ magnified, real
