The Law of Reflection
An inspection of the data above reveals that there is no clear linear relationship between the angle of incidence and the angle of refraction. For example, a. Snell's law is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through. Normal Angle of Incidence Angle of Reflection Reflected Ray Incident Ray i r' Used to describe the relationship between the angle of incidence and refraction, Step 1: Draw a diagram (trust me this will help) Step 2: Write down the values.
This line is known as a normal line labeled N in the diagram.
The normal line divides the angle between the incident ray and the reflected ray into two equal angles. The angle between the incident ray and the normal is known as the angle of incidence.RELATION BETWEEN REFRACTIVE INDEX AND CRITICAL ANGLE
The angle between the reflected ray and the normal is known as the angle of reflection. These two angles are labeled with the Greek letter "theta" accompanied by a subscript; read as "theta-i" for angle of incidence and "theta-r" for angle of reflection.
The law of reflection states that when a ray of light reflects off a surface, the angle of incidence is equal to the angle of reflection. Reflection and the Locating of Images It is common to observe this law at work in a Physics lab such as the one described in the previous part of Lesson 1. To view an image of a pencil in a mirror, you must sight along a line at the image location.
- The Law of Reflection
- The Angle of Refraction
- Snell's Law
As you sight at the image, light travels to your eye along the path shown in the diagram below. The diagram shows that the light reflects off the mirror in such a manner that the angle of incidence is equal to the angle of reflection.
It just so happens that the light that travels along the line of sight to your eye follows the law of reflection. The reason for this will be discussed later in Lesson 2.
If you were to sight along a line at a different location than the image location, it would be impossible for a ray of light to come from the object, reflect off the mirror according to the law of reflection, and subsequently travel to your eye.
Only when you sight at the image, does light from the object reflect off the mirror in accordance with the law of reflection and travel to your eye. This truth is depicted in the diagram below. For example, in Diagram A above, the eye is sighting along a line at a position above the actual image location. For light from the object to reflect off the mirror and travel to the eye, the light would have to reflect in such a way that the angle of incidence is less than the angle of reflection.
In Diagram B above, the eye is sighting along a line at a position below the actual image location. In this case, for light from the object to reflect off the mirror and travel to the eye, the light would have to reflect in such a way that the angle of incidence is more than the angle of reflection. Neither of these cases would follow the law of reflection. In fact, in each case, the image is not seen when sighting along the indicated line of sight.
It is because of the law of reflection that an eye must sight at the image location in order to see the image of an object in a mirror.
Check Your Understanding 1.
The Angle of Refraction
Consider the diagram at the right. This is as illustrated in the figure below. The dotted line represents the undeviated direction of the ray if the prism was no there.
Of course, this is the minimum value of angle of deviation.
At the minimum deviation angle, the angle of incidence and the angle of emergence of the ray are identical. As you can see from the above figure, this will occur only if the light ray inside the prism passes parallel to the base of the prism you can prove it from the prism equation. Also, this angle of deviation happens only for a particular angle of incidence.
Optics Reflection, Refraction & Snell’s Law Lesson 2
When a ray of light is incident obliquely on the interface of another medium, refraction happens. However, if the ray of light is incident normally on the interface, then refraction will not happen actually the refraction is always there and in this particular scenario, the angle of refraction becomes zeroand the the ray of light passes undeviated through the prism, leaving the angle of deviation zero.
This is the normal position. When you rotate the prism about an axis passing perpendicular to the plane of incidence, then you can see that the angle of deviation changes with change in angle of incidence and finally reaches a minimum value and after that it increases again on further rotation in the same direction.
If the incident light beam is rotated in either direction from the minimum deviation position, the deviation of the light from its incident path caused by refraction in the prism will be greater.