Lenses Flashcards
What is refraction?
Refraction is the change of direction of light as it passes from one medium (substance) to another. The two media must have different densities, such as air and glass.
What happens if rays of light cross the boundary at 90°?
Refraction does not happen. It passes through in a straight line.
What is a refractive index?
The degree to which a material slows the speed of light (compared to its speed in a vacuum) is its refractive index.
What is the equation for calculating a refractive index?
refractive index = sin i/sin r
What are the two types of lenses?
converging and diverging
What is a converging lens?
A converging lens is curved outwards on both sides. It is represented on diagrams by the symbol.
What is a diverging lens?
A diverging lens is curved inwards on both sides. It is represented on diagrams by the symbol
What is the focal length?
The focal length is the distance between the centre of the lens and the virtual image.
What is a virtual image?
A virtual image is an image that cannot be projected onto a screen.
What is the principal focus?
The point at which the rays appear to have come from is the principal focus
