8TH GRADE · LIGHT PHENOMENA
Refraction and lenses
Changing the direction of light, focusing the lens and constructing images.
The entire theory of the lesson is collected here; you can read it without an account. In interactive mode, the same theory appears as cards, followed by questions. with checking the answer and task, and progress is saved.
Basic Concepts
Refraction of light
When passing between transparent media, a light beam usually changes direction due to a change in the speed of light.
The beam deviates towards the perpendicular when passing into an optically denser medium, and away from it into a less dense one.
Lens and its focus
A lens is a transparent body with refractive surfaces that collects or scatters passing rays.
A converging lens brings parallel rays together at a real focus, while a diverging lens has an imaginary focus.
Lens power
Optical power characterizes the refractive effect of a lens and is numerically equal to the reciprocal of its focal length.
A converging lens has a positive optical power, a diverging lens has a negative optical power; The unit of measurement is called diopter.
Physical quantities
Focal length
The distance from the optical center of the lens to its main focus.
Unit: meter ·
Tasks on the topic
Statements, answer options and the walkthrough.