11TH GRADE · OPTICS
Lenses and diffraction
Lens formula, magnification, optical power and diffraction grating.
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
Thin Lens
A transparent optical body whose thickness can be neglected in calculations.
The lens collects or scatters rays; Using the signs of the distances in the formula, you can determine whether the image will be real or imaginary.
Diffraction grating
A periodic structure of a large number of equally spaced slits or streaks.
Waves from multiple slits interfere: bright main maxima appear only at certain angles.
Physical quantities
Focal length
The distance from the optical center of the lens to the main focus.
Unit: meter ·
Distance to object
Distance from lens to object.
Unit: meter ·
Image distance
Distance from lens to image.
Unit: meter ·
Optical power
The reciprocal of the focal length of the lens.
Unit: diopter ·
Linear increase
The ratio of image size to object size.
Unit: dimensionless quantity
Image height
Linear size of the image.
Unit: meter ·
Item height
Linear size of an object.
Unit: meter ·
Diffraction grating period
The distance between adjacent grating lines.
Unit: meter ·
Diffraction angle
Angle of direction of the diffraction maximum.
Unit: radian ·
Maximum order
The integer number of the diffraction maximum.
Unit: dimensionless quantity
Lesson formulas
Thin Lens Formula
The optical system relates the focal length to the distances to the object and the image.
Lens power
Optical power is the inverse of focal length in meters.
Determination of diopter
One diopter is equal to a reciprocal meter.
Linear lens magnification
Linear magnification is equal to the ratio of the dimensions of the image and the object and the ratio of the corresponding distances.
Diffraction grating formula
The position of the main maxima is determined by the grating period, angle, order and wavelength.
Related formulas
The same formulas in the reference, with symbols and units.
Tasks on the topic
Statements, answer options and the walkthrough.