Vergence and focussing Flashcards
(23 cards)
What is vergence in optics?
The curvature of a light wavefront.
Vergence is a key concept in understanding how light behaves as it passes through different optical surfaces.
What is the formula for calculating image vergence (Lā)?
Lā = L + F
Where L is the object vergence and F is the focal power of the surface.
Define object vergence.
The curvature of the light wavefront that is incident on the focal surface or lens.
Define image vergence.
The curvature of the light wavefront that leaves the focal surface or lens.
What is the focal power of a surface?
A measure of how much it changes the object vergence.
What is the relationship between radius and curvature?
There is an inverse relationship between radius and curvature.
What is a real object in optics?
One from which light diverges, often represented by a point source of light.
True or False: Light from a point source diverges in all directions.
True
What must distances be measured in for the answer to be in Dioptres?
Metres
What does an optical surface with focal power do to incident light?
It changes the vergence of the incident light by either adding convergence or divergence.
What is the sign of the radius of curvature for a convex surface?
Positive
What is the sign of the radius of curvature for a concave surface?
Negative
If the object is real and adding convergence, what are the possible outcomes for image vergence?
- The image vergence is converging
- The image vergence is diverging
- The image vergence is zero
What is the outcome when adding divergence for a real object?
The image vergence is diverging.
What is required to form a real image of a real object?
You must add convergence greater than the value of the incident vergence.
Fill in the blank: A convex spherical refracting surface separating air from glass has a radius of curvature of ______.
12cm
What happens to vergence as light moves away from a point source?
Its vergence changes.
What is the vergence value for light from a real object?
Negative
What does the sign convention imply for distances in optics?
Distances are measured from the optical surface/lens to the object point or image point.
What is the vergence of light from a real object?
Negative value of object vergence.
What is the significance of the focal power in optics?
It determines how much the surface changes the vergence of light.
True or False: Real objects can have a positive value of object distance.
False
What is indicated by a negative value of vergence?
Light is diverging.
