Optics Flashcards
What is the basic law of reflection?
The angle of incidence is equal to the angle of reflection (within the same medium).
When a light ray changes mediums from n1 to n2, how does it’s velocity and angle change when n1 < n2 and when n1>n2?
For n1<n2;
velocity decreases and the angle bends toward the normal
For n1>n2;
velocity increases and the angle bends away from the normal
What is a refractive index?
It is a measured factor of how light’s speed decreases in different mediums
What is a critical angle?
It is the incident angle at which a light ray at a boundary bends along the surface between two mediums. (Note: n2 < n1// initial n must be greater than the other)
What if the angle of incidence is greater than the critical angle?
The light undergoes total internal reflection and not refraction
Where is the focal point for a concave mirror and for a convex mirror?
For a concave mirror, it is in front of the mirror. (f is +’ve)
For a convex mirror it is behind the mirror. (f is -‘ve)
Where is the image if the object distance from a concave mirror is equal to the focal length?
The image is at infinity, it can’t be observed.
Where is the focal point on a converging lens?
The focal point is always opposite of where the rays enter the lens. (f is +ve)
In the Lensmaker’s equation, how does the radius of curvatures sign change depending on the face shape (concave or convex) and type (lens or mirror)?
For convex lens faces and concave mirror faces, the radius of curvature is positive.
For concave lens faces and convex mirror faces, the radius of curvature is negative.
What are spherical aberrations and what are solutions to them?
Spherical aberrations occur when a mirror can’t converge all the rays to focal point with precision. So parabolic mirrors or Schmidt corrector plates are used to fix the issue.
Why do chromatic aberrations occur and how can they be fixed?
Chromatic aberrations occur with white light being refracted. The various colours in have different refractive indexes so they bend at different angles. So a achromat, a pair of lenses with different dispersions, must be used to correct this.
What is a near point?
This is the closest distance our eyes can see an object clearly. Our eyes change curvature to see closer or further.
What’s the difference between Myopia and Hyperopia?
Myopia - seeing distant objects is difficult and blurry. Diverging lenses correct this issue.
Hyperopia - seeing close objects is difficult so converging lens is needed to correct it.
Describe a refracting telescope.
This is a lens system of two converging lens placed so focal points meet and form an observable image smaller than the object
Describe a reflecting telescope.
A spherical mirror bends light entering the telescope inward and has a plane mirror direct the light to an eye.
