 # Law of reflection of light

Article about Law of reflection of light

Definition of reflection

Reflection can be interpreted as an event in which the direction of motion of an object changes due to the object hits a barrier. If you throw a ball on the wall, the ball reflected because the ball hits the wall.

Reflection of light

When light is emitted by the sun or other light sources such as electric lights, light moves from the light source in all directions. When light strikes a barrier such as a book, wall or mirror, light is reflected by that barrier. The direction of the light reflection after it strikes a barrier object is different from the direction of motion of the light before it strikes the barrier. It can be said that the reflection of light is an event in which light strikes a barrier so that the direction of light changes; the direction of movement of light after strikes a barrier object is different from the direction of motion of light before strikes a barrier.

The law of reflection of light

The law of reflection of light is a physics law that explains the event of reflection of light. You can prove this law by conducting a light reflection experiment. Following is the statement of the law of reflection of light:

1. Incident light rays (p), reflected light rays (q) and the normal to the surface (N) lie in the same plane. p = Incident light rays, q = reflected light rays, i = angle of incidence, r = angle of reflection, N = normal to surface

Incident light rays

Incident light rays are beams of light that move towards a barrier object. If the barrier object is a book, the incident light rays are beams of light moving towards the book. If a barrier object is a mirror, the incident light rays are beams of light that move toward the mirror.

Reflected light rays

Reflected light rays are beams of light that move away from the barrier object after strike the barrier.

Normal to surface

The normal line is an imaginary line perpendicular to the surface of the barrier object hit by a beam of light. If the barrier object is a mirror, the normal line is an imaginary line perpendicular to the mirror surface through which the beam of light passes.

Plane

Plane are flat surfaces and have certain limits. The plane can also be interpreted as the surface area. Observe the figure. If you put a sheet of paper vertically so that it coincides with the incident light rays, reflected light rays and the normal line then the surface of the paper,

lies in a flat plane with the incident light rays, reflected light rays and normal line. Likewise with Figure 2. If you place a piece of paper vertically so that it coincides with the incident light rays,

reflected light rays and the normal line then the surface of the paper lies in a flat plane with the incident light rays, reflected light rays and normal line.

2. The angle of incidence is the same as the angle of reflection

If the angle of incidence is 30o, the angle of reflection is 30o. If the angle of incidence is 90o (the direction of motion of the ray comes perpendicular to the surface of the object), the angle of reflection is 90o

(the direction of the reflected light is perpendicular to the surface of the object but opposite and coincides with the direction of the incident light rays).

1. What is the law of reflection of light?

The law of reflection states that the angle of incidence (i) is equal to the angle of reflection (r), i.e., i = r. Furthermore, the incident ray, the normal at the point of incidence, and the reflected ray all lie in the same plane.

2. What role does the normal play in the law of reflection?

The normal is a line perpendicular to the surface at the point of incidence. It serves as the reference line from which the angles of incidence and reflection are measured.

3. Is the law of reflection valid for both smooth and rough surfaces?

Yes, the law of reflection is valid for both smooth and rough surfaces. However, for rough or irregular surfaces, because the normals at different points of incidence are different, the reflected rays scatter in different directions. This phenomenon is known as diffuse reflection.

4. Why does an object appear to be reversed in a mirror according to the law of reflection?

When light rays reflect off a flat mirror, the angle of incidence equals the angle of reflection. However, our brain interprets these rays as coming straight from behind the mirror, resulting in a virtual, laterally inverted image.

5. Does the color of light affect the law of reflection?

No, the color of light does not affect the law of reflection. Regardless of the color, or equivalently the wavelength, of the light, the angle of incidence always equals the angle of reflection.

6. How is the law of reflection applied in periscopes?

A periscope works on the principle of successive reflections. There are two mirrors placed parallel to each other at 45°. Thus, a ray of light entering the periscope reflects twice and changes its path by 180°, enabling the viewer to see objects not directly in their line of sight.

7. How does the law of reflection explain the working of a plane mirror?

A plane mirror produces a virtual, upright, and laterally inverted image due to the law of reflection. Each ray of light incident on the mirror is reflected such that the angle of incidence equals the angle of reflection, and this leads to the formation of the image behind the mirror.

8. How is the law of reflection used in the design of rearview mirrors in vehicles?

Rearview mirrors are slightly curved (convex) to provide a wider field of view for the driver. The law of reflection still applies at each point on the mirror’s surface, and by adjusting the angle of the mirror, the driver can see a panoramic view of the traffic behind them.

9. How does the law of reflection aid in the formation of a rainbow?

Rainbows are caused by a combination of refraction and reflection of light inside water droplets. The law of reflection helps in explaining the internal reflection of light within the droplets, which along with dispersion of light, leads to the formation of the colored spectrum of a rainbow.

10. Why is the law of reflection integral in optical fiber technology?

Optical fibers work on the principle of total internal reflection, a phenomenon that relies on the law of reflection. The law of reflection ensures that light signals can travel long distances within the fiber with minimal loss of signal strength.