11TH GRADE · OPTICS
Reflection and refraction of light
Laws of reflection, refraction and total internal reflection.
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
Law of Light Reflection
The incident and reflected rays lie in the same plane with the normal, the angle of reflection is equal to the angle of incidence.
Both angles are measured from the normal to the surface, and not from the surface itself - this is a common source of error.
Law of light refraction
Relationship between the angles of incidence and refraction with the optical properties of two media.
When crossing the boundary, the frequency of light does not change, but the speed and wavelength change; so the beam turns.
Total internal reflection
Reflection of light from a boundary without a refracted ray upon transition from an optically denser medium.
It is possible only upon transition from an optically denser medium to a less dense one and at an angle greater than the limiting one.
Physical quantities
Angle of incidence
The angle between the incident ray and the normal to the boundary.
Unit: radian ·
Reflection angle
The angle between the reflected ray and the normal to the boundary.
Unit: radian ·
Angle of refraction
The angle between the refracted ray and the normal to the boundary.
Unit: radian ·
Relative refractive index
The ratio of the refractive indices of two media.
Unit: dimensionless quantity
Refractive index of the first medium
Optical characteristics of the first medium.
Unit: dimensionless quantity
Refractive index of the second medium
Optical characteristics of the second medium.
Unit: dimensionless quantity
Limit angle of total reflection
The smallest angle of incidence at which total internal reflection begins.
Unit: radian ·
Lesson formulas
Law of Reflection
The angle of reflection is equal to the angle of incidence.
Law of refraction
The ratio of the sines of angles is related to the refractive indices, velocities and wavelengths in the media.
Limit angle of total reflection
The sine of the limiting angle is equal to the inverse relative refractive index.
Condition: Light comes from an optically denser medium to a less dense one.
Related formulas
The same formulas in the reference, with symbols and units.
Tasks on the topic
Statements, answer options and the walkthrough.