Light refractation

Содержание и основные понятия

At the boundary of the medium, the speed of light changes, so the beam is usually rejected.
GEF · Grade 8
PIF · Baseline
Interactive model
fracture
Refrigeration rate
normal
Full reflection
01
The physical picture
What happens and what boundaries the model has.
Main message
At the boundary of the medium, the speed of light changes, so the beam is usually rejected.
When moving into an optically denser environment, the beam deviates to normal.
The frequency of light at the border does not change, and the speed and length of the wave change.
Full internal reflection is possible with a sufficiently large coal.
How to reason
First, name the system and the interaction, then select the values, and only then write down the law. The formula works within the model's assumptions.
02
Laws and values
Symbols should be read as a relationship of values, not as a recipe for substitution.
n
=
c
v
n=\frac{c}{v}
n
=
v
c
​
absolute refractation rate
n
1
sin
⁡
α
=
n
2
sin
⁡
β
n_1\sin\alpha=n_2\sin\beta
n
1
​
sin
α
=
n
2
​
sin
β
Refraction law
Review of the situation
The depth of the basin appears to be smaller than the real one: the rays from the bottom break down at the water-air border.
04
Links and application
In the real world
The depth of the basin appears to be smaller than the real one: the rays from the bottom break down at the water-air border.
Model verification
Compare the prediction with observation, evaluate the units, the order of magnitude and the influence of the factors not taken into account. Disparity does not always mean an error of law: often idealization is no longer sufficient.
C
What needs to be understood
Outcome 1
Explain the physical meaning of the topic "Light Break" through the model, not just through the formula.
Outcome 2
To distinguish and correctly use terms: refractation, refractive indicator, normal.
Outcome 3
Indicate the conditions for the applicability of the law, verify units and limit cases.
T
Terms of the topic
The definition should indicate the physical meaning, not a substitute for a domestic synonym.
fracture
Changing the direction of wave spread between environments at different speeds.
Refrigeration rate
The ratio of the speed of light in a vacuum to the phase speed of the light in the environment.
normal
Straight, perpendicular to the surface at the point of the beam drop.
Full reflection
The reflection of the wave from the border without a refracted spreading beam at the coal is more critical.
F
Origin and conclusion of the formulas
The fundamental law cannot be "proven" by algebras: for each record, it is stated whether it is a definition, an experimental law, or a model effect.
n
=
c
v
n=\frac{c}{v}
n
=
v
c
​
definition
Absolute refractation rate.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
c
=
скорость света в вакууме
c=\text{скорость света в вакууме}
c
=
speed
Light
in
vacuum
The speed of light in the vacuum is chosen as the reference.
n
=
c
v
n=\frac{c}{v}
n
=
v
c
​
The absolute refrigeration indicator shall be entered as the ratio of reference speed to the phase speed of the light in the environment.
Conditions:
The uniform transparent medium and the specified frequency of light; v is the phase speed, and at variance n depends on the length of the wave.
Monitoring:
The dimensions of both parts shall coincide; the result shall be checked for sign, order and limit case.
n
1
sin
⁡
α
=
n
2
sin
⁡
β
n_1\sin\alpha=n_2\sin\beta
n
1
​
sin
α
=
n
2
​
sin
β
empirical law
The law of refractation.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
α
=
∠
(
падающий луч
,
нормаль
)
,
β
=
∠
(
преломлённый луч
,
нормаль
)
\alpha=\angle(\text{падающий луч},\text{нормаль}),\quad \beta=\angle(\text{преломлённый луч},\text{нормаль})
α
=
∠
(
Falling
beam
,
normal
)
,
β
=
∠
(
Refrigerated
beam
,
normal
)
Both angles are measured from normal to section boundary.
sin
⁡
α
sin
⁡
β
=
n
2
n
1
\frac{\sin\alpha}{\sin\beta}=\frac{n_2}{n_1}
sin
β
sin
α
​
=
n
1
​
n
2
​
​
The experience of Snellius establishes the continuity of sinus relationships for two media and one frequency.
n
1
sin
⁡
α
=
n
2
sin
⁡
β
n_1\sin\alpha=n_2\sin\beta
n
1
​
sin
α
=
n
2
​
sin
β
Symmetrical recording reflects the same empirical law of refractation.
Conditions:
Flat boundary of homogeneous isotropic media, monochromatical light, geometric optics; with complete internal reflection of the refracted beam, no.
Monitoring:
The dimensions of both parts shall coincide; the result shall be checked for sign, order and limit case.
!
Model boundaries and typical errors
Error: Forget model condition
You can't move the formula to any situation just because it's a coincidence of letters. The key condition of this topic is that when you move into an optically denser environment, the beam deviates to normal.
How to Check the Mind
The frequency of light at the border does not change, and the speed and length of the wave changes. Then check the units, the direction of the vectors and the behaviour of the result at zero or very large parameter.
Σ
Conclusion on the topic
Light refractation
At the boundary of the medium, the speed of light changes, so the beam is usually rejected.
When moving into an optically denser environment, the beam deviates to normal.
The frequency of light at the border does not change, and the speed and length of the wave change.
Any numerical result shall be accompanied by a unit, a sign and an explanation of its physical meaning.
The content is consistent with the FRP on Physics of the OS/OSS 2025 and the subject matter of the current lines of the PNP: I. M. Peryškin and co-authors (7–9), G. J. Mäkishev and coauthors (10–11), and with the lines "Engineers of the Future" and V. A. Kasyanov. The original texts are not reproduced, the text of the textbooks is not reproduced.