Astrophysics Flashcards
What is the definition of a ray?
A representation of a light path
What is the definition of the normal line on a ray diagram?
The line perpendicular to the surface
What is the definition of the plane on a converging and diverging ray diagram?
The line drawn that is in the centre of your lens
What is the definition of the principal axis on a converging and diverging ray diagram?
The line that passes through the centre of the lens, perpendicular to its surface
What is the definition of the focal point on a converging and diverging ray diagram?
This is the point (drawn where your principal axis and plane intersect) where incoming rays travelling parallel to the principal axis will be refracted and converge/ are directed away from one another
What is the definition of divergence?
Light rays that spread apart over a distance/ spreads out incident light
What is the definition of convergence?
Light rays that come together over a distance/ focuses incident light
What is the definition of a real image?
A projected image formed from light focussing/crossing each other after refraction
What is the definition of a virtual image?
An apparent image formed on the same side of the lens - since the light rays are not focussed/ do not cross the image cannot be projected onto a screen
Which type of image can be formed on a screen?
A real image
In which type of lens are real images usually formed?
Converging lenses
In which type of lens are virtual images usually formed?
Diverging lenses - however, can be produced by converging lenses
When will a converging lens never form an image?
This is when your object is placed at your focal length - your refracted rays will be parallel to on another
When will a converging lens form a virtual image?
This is when your object is placed at a distance that is less than your focal length - your refracted rays will diverge hence you draw a dashed line backwards from them to find where your virtual image would form
What is the definition of focal length?
The distance between the centre of your lens and the principal focus
What are the 3 rays that you have to draw a converging and diverging ray diagram?
- Centre ray
- Parallel ray
- Focus ray
What is the definition of your centre ray on a converging and diverging ray diagram?
The ray that runs through the centre of your lens/ mirror curvature and does not deviate/ get refracted
What is the definition of your parallel ray on a converging and diverging ray diagram?
The ray that is drawn parallel to your principal axis that always goes through your principal focus, f:
- If your rays converge then your parallel ray will go through the principal focus on the opposite side of your object
- If the rays diverge then your parallel ray will go through the focus on the same side as your object (this focus is also focal length distance away from the centre of the lens)
What is the definition of your focus ray on a converging lens ray diagram?
The ray that runs through your focal point on the same side as your object and is then refracted parallel at the plane of your lens
What does a converging lens look like?
Has 2 convex lines facing outwards
How do you show where an image will be formed on a converging and diverging ray diagram?
Draw a line down to the principal axis from where the lines converge (real or virtual)
Where are your foci on a ray diagram?
Your foci are drawn on either side of your lens and are equidistant from one another and from the centre of the lens
What is the definition of your focus ray on diverging lens ray diagram?
The ray that runs through the principal focus virtually as it gets refracted parallel at the plane of the lens before it reaches this focus
What does a diverging lens look like?
Has 2 concave lines facing outwards