Laws of Reflection - Definition, Diagram, Examples, FAQs

State the Laws of Reflection.

According to the law of reflection, when a ray of light reflects off a surface, the angle of incidence is equal to the angle of reflection.
The reflected ray always meets the surface normal at the point of contact between the incident ray and the plane defined by the incident ray and the surface normal.
A plane mirror or curved mirror produces images that are explainable by the law of reflection. The laws of reflection hold good for light reflected from any smooth surface.

Reflection law can be defined as:

An incident ray, a reflected ray, and the surface's normal lie in the same plane when they fall on a smooth surface; also the angles of reflection and incidence are equal. The beam of light striking the reflecting surface is called the incident ray.

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Reflection of light: what is it?

Reflection occurs when light traveling through one material bounces off a different material. The reflected light still travels in a straight line, only in different directions. It depends on the interface if the light is specular (mirror-like) or diffuse (keeping the energy but losing the image).

Reflection of specular light occurs through a mirror, which is usually made up of a glass sheet with a metallic coating that captures the light. As waves propagate beyond their skin depths, metals exhibit enhanced reflection.

Diagram of specular reflection

Using the diagram, a vertical mirror O is struck by a light ray PO, producing reflected light OQ. The reflection of light can happen when light travels from a medium whose refractive index is one of the means of propagation into another medium whose refractive index is different, for reflection examples. It is generally true that in the most general case, some of the light is reflected and the remainder is refracted.

By putting Fresnel's equations into practice for a light ray striking a boundary, it is possible to determine what percentage of the light is reflected and for what percentage it is refracted. Analogous to the way impedance mismatches cause signals to be reflected in electric circuits.

An angle of incidence greater than the critical angle will result in a total internal reflection of light from a denser medium.

Reflection light of high refractive index materials shifts it 180° relative to the medium traveling. The reflected light is phase-aligned with the incident light when it reflects off a material with a lower refractive index. Thick-film optics uses this principle to explain many of its basic principles.

An image is formed by specific reflections. If we rotate the image, we see, the image appears reversed, as if it had been reflected from a flat surface. A curved mirror may have optical power; curved reflections form images that may be magnified or demagnified. Typically, spherical or parabolic mirrors have spherical or parabolic surfaces.

The difference between regular and irregular reflection

Concave Mirrors:

If an object lies beyond the focus of the mirror, then concave mirrors produce actual, inverted images, while a virtual, erect, enlarged image appears when the object lies closer to the focus.

Concave mirrors have the following uses:

• Torches, searchlights, and the headlights of vehicles have been using concave mirrors for years to produce parallel beams of light.
• In addition to shaving mirrors, concave mirrors are also used to view the face more clearly.
• Dentists use concave mirrors to examine a patient's teeth in greater detail.
• Solar furnaces use concave mirrors to concentrate the sun's energy to produce heat.

Mirrors with convex surfaces:

The result is always a mirror image that looks erect and diminished.

Convex mirrors have the following uses:

• In vehicles, convex mirrors are used as side-view mirrors to see vehicles coming from behind in a smaller field of view.
• Magnifying glasses and telescopes are often manufactured with convex mirrors.
• Street lights are reflected by convex mirrors since they can illuminate a wide area.
• A convex mirror is placed at the corners of the street to prevent accidents.

Reflecting on the whole process:

If light passes from a denser medium to a lighter medium at an angle greater than the critical angle necessary for refraction, it will reflect into a denser medium. Total Internal Reflection refers to this phenomenon. The ordinary laws of reflection for light also govern light that undergoes a total internal reflection:

A curved path is created by the phenomenon of total internal reflection. Fibre-air interfaces are large enough to cause light reflected from narrow fibres of glass or plastic to repeatedly exceed the critical angle. Light can be transmitted over long distances without losing intensity when it passes through optical fibres.

An optical fibre network uses pulses of light to transmit information using total internal reflection. An optical fibre bundle is used by instruments such as endoscopes to image internal organs through total internal reflection.

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Reflection's benefits include:

Periscopes use reflection to observe advancing enemies on the battlefield from a safe distance.

We see objects because of reflections.

As mentioned above, mirrors with concave and convex surfaces can reflect a variety of different images.

Medical diagnostics rely on reflection, as does optical communication.

The law of reflection governs both light and sound, as both are waves.

Our ability to measure distances accurately to objects is based on the law of reflection for sound and light.

The echoes of sound are the result of reflections.

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Reflection Laws Reflection Examples

Q1. An incident ray of light strikes a plane mirror at an angle of 30° with the mirror surface. Approximately what angle will the reflection be?

Ans: The angle of incidence is determined by comparing the incident ray with the normal, so it is not 60° in this case

Following the Law of reflection,

θ i = θ r

Hence,

The angle of reflection = 600

Q2: Determine the angle * which would be made by the system of the two mirrors shown in the figure below so that A and B are parallel to one another.

Ans: Here is a diagram in which we fill in the angles of incidence and reflection and also label the rays as they are incident and reflected.

Angles I + r and i' + r’, which represent the incident wave at A and the reflected wave at B, have to be supplementary. (Geometry: cross-section cut between parallel lines).

Therefore,

i + r + i’+ r’ = 180 °

As a result of the law of reflection, i = r and r' = i'

Substitute to obtain

i + i + i’ + i’ = 180 °

i + i’ = 90

In triangle AOB, we have

α + (90 – r) + (90 – i’) = 180 °

α = r + i’ = i + i’ = 90 °

If α = 90 °, the downward ray passes through A and the upward ray passes through B.

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