Light
Progress of the light
When I pass the same material, the going straight … light of the light goes straight on without turning. The speed is 300,000km/s in vacuo. When I advance in water and a material such as the glass, it becomes later than this.
The object which gives source of light … oneself light.
An example: candle flame, electric bulb, the sun
※The reason to see a thing is because light enters the eyes. The light that the sun and an electric bulb gave off reflects that it sees the object which does not give light by oneself at the surface of the object, and this is because it reaches the eyes.
Reflection of the light
Reflection of light … light go over in an object.
law of reflection…When light is reflected on a flat surface, the incident angle and the reflection angle are equal.
Normal…A line that passes through the point where light hits and is perpendicular to the plane.
incidence angle…The angle between the incident light and the normal.
reflection angle…Angle formed by reflected light and normal.
Refraction of the light
A phenomenon to bend on a boundary surface when I advance from a material with the refraction … light of the light to the different material. But an incidence angle is not refracted at the time of 0 degrees, and the light goes straight on.
※A part of the light is refracted, and a part may reflect it. In that case, quantity of the light decreases because light is divided.
When light is incident from all over the air underwater
It is an incidence angle in this way＞It becomes the refraction angle.
When light is incident in the air from the water
It becomes the incidence angle <refraction angle in this way.
In the refractive index … chart below
The phenomenon that a refraction angle puts it away more than 90 degrees at time beyond the angle with the incidence angle when total reflection … light advances into air from water and glass, and the light reflects all it without being distorted.
An example of the total reflection: Optical fiber, endoscope
※The total reflection is an incidence angle like water from all over the air＞When it becomes the refraction angle, it is not generated.
When light is the object that the diffused reflection … surface was uneven and reflects it, reflect the light in the various directions.
An example of the diffused reflection: A wave shines by solar light to a bright shine
Problem of the drawing figures
I show below the pattern of the problem that is easy to be relatively made questions for by a problem of the drawing figures of the light.
①Parallelism flat glass
[exercise]
In the next figure, I choose the route to advance of right light among a~c, and write a route of the light before being able to let glass, and leaving in the air.
[solution]
When light advances to glass from all over the air, as for the answer, it is with a route of a in the refraction angle becoming smaller than an incidence angle. In addition, the light to shoot it, and to perform appearance from light and glass before being incident on glass becomes parallel. Based upon the foregoing, the light follows the route such as the chart below.
②Hemicycle glass
[exercise]
In the next figure, I choose the route to advance of right light among a~c, and write a route of the light before being able to let glass, and leaving in the air.
[solution]
①When it is the same as の parallelism flat glass, and light advances to glass from all over the air, as for the refraction angle, as for the answer, it is with a route of a because I become smaller than an incidence angle. In addition, I go straight to it without being refracted in one (incidence angle 0 degrees) of that light leaves for an aspect perpendicularly to show it to the chart below when I shoot appearance from glass in the air and do it. Based upon the foregoing, the light follows the route such as the chart below.
③The coin that it seems that I become alienated
[exercise]
In the next figure, write a route of the light before the light that came out of a coin in the water reaching the eyes.
[solution]
I show an answer in the chart below. The forms are as follows.
① I tie up a mesh to the coin which I become alienated, and is obvious by a straight line
② ①Because の line and the point of intersection with the surface of the water become the refraction point, I pull a line by the order called coin → refraction point → eyes of the real position. This becomes the answer.
※Because it touches an eye from a coin, the light will prevent you from forgetting that you show an arrow as well as a straight line in a figure.