Reflection of Light – Laws, Types, Applications, & FAQs

Introduction

Have you ever looked into the mirror and wondered why our reflection stares back at us so perfectly or noticed how clouds appear white in daylight and dark at night? Even when we see ourselves on the water, we are able to see our reflection but not quite as perfect as that of a mirror. This all is possible due to the fascinating phenomenon of Reflection of light. Light usually  travels in straight lines, but it changes its path when it strikes a surface, this is called reflection. The laws of reflection explain how light bounces off surfaces, forms images, admires the glow of sunlight or calm moon on the water surface and even helps us to design different devices like optical fibres, periscopes, reflectors, and telescopes.

Reflection is the reason we are able to see things around us. The ray of light strikes the object and then comes to our eyes, hence we are able to see that object. One important thing to remember is that the process of reflection takes place in the same medium. If an object lets the light pass through it completely then we cannot see that object, for example air. In order to be visible to the human eye, an object must reflect light either fully or partially.

Statement of Laws of Reflection

These are the two universal laws of reflection – they hold true for all types of reflecting surfaces.

Terms used in Laws of Reflection

There are some terms which students should know before moving further to learn Laws of Reflection.

• Incident Ray: – The incoming ray of light from the source of light which strikes a surface.
• Point of incidence: – The exact point where the incident ray, reflected ray and normal hits the surface.
• Normal: – An imaginary line drawn perpendicular to the surface at the point of incidence.
• Reflected Ray: – The ray of light that bounces back from the surface at the point of incidence.
• Angle of incidence: – The angle between the incident ray and the imaginary normal is called an angle of incidence.
• Angle of reflection: – The angle between the reflected ray and the imaginary normal is called an angle of reflection.
• Plane of incidence: – The plane containing the incident ray, reflected ray, and the normal.
• Smooth surface: – A polished surface like a mirror where regular reflection occurs.
• Rough surface: – An uneven surface where irregular reflection occurs.
• Image: – The visual reproduction formed by reflected rays (can be real or virtual).

Conditions for the law of reflection to hold

Usually, reflection from any surface can be observed. However, we are not able to see it clearly unless the reflecting surface is smooth. There are some points which will help to make the image formation to be clear and predictable, if it suffices these following conditions.

• The reflecting surface should be smooth and polished.
• The incident ray should strike the surface in a defined direction.
• The medium on both sides of the surface should be uniform (like air). If it is non-uniform we will see the refraction of light.

Types of Reflection

Before we dive into the real life examples of reflection, it’s important to understand that reflection doesn’t happen in the same way. The nature of the reflecting surface plays a vital role in reflecting light and making an image, which usually is seen behind the mirror. Depending on the types of reflecting surface, there are two types of reflection:

1. Regular reflection

• When all the reflected rays from the reflecting surface are parallel to each other, this is called regular reflection.
• Occurs on smooth and polished surfaces like mirrors.
• It produces a clear and sharp image that appears behind the reflecting surface, such as in a mirror or calm water.

2. Irregular reflection

• Happens on rough or uneven surfaces like walls, paper, or the ground.
• The reflected rays scatter in many directions. 
• No clear image is formed 

Everyday examples of Reflection of light

• Mirrors: When you stand in front of a bathroom mirror, or you see in your vehicle mirror you are able to see the image clearly because light reflects smoothly off its polished surface.
• Jewelry: We see several ornaments shining, that is because of the polished surface and they do reflect a lot of light when kept under the light source.
• Calm Lake or Pond: On a still day, trees and mountains appear almost perfectly on the water surface. The smoothness of the water allows parallel reflection, much like a natural mirror. 
• Rough wall in Sunlight: When sunlight strikes a brick wall, the uneven surface scatters the light in all directions. This scattering prevents any clear image from forming but makes the wall visible from every angle.
• Car Headlights on a Wet Road: At night, car headlights shining on a wet or rough road spread out irregularly. This scattered reflection reduces clarity but helps drivers see the road surface.

Applications of Reflection in Technology

Reflection of light is not just limited to mirrors or water—it plays a vital role in many modern technologies:

Mirrors and Reflectors:

• Plane and curved mirrors are used in homes, vehicles, and instruments for clear image formation.
• Bicycle and car reflectors use reflection to bounce back light for road safety.

Optics Fibers:

• Plane Optical fibers work on the principle of total internal reflection.
• They are widely used in high-speed internet, communication, and medical endoscopy.

Periscopes

• Periscopes use plane mirrors placed at angles to reflect light and allow people to see over walls or obstacles.
• Common in submarines and defense applications.

Telescopes and Microscopes

• Reflecting telescopes use curved mirrors to gather and focus light from distant stars.
• Microscopes use reflection along with lenses to magnify tiny objects.

Laser Devices and Scanners

• Reflection guides laser beams in printers, barcode scanners, and medical surgeries.
  

Solar Cookers and Panels

• Concave mirrors reflect and concentrate sunlight to generate heat in solar cookers.
• Reflective coatings in solar panels improve efficiency by directing more light into the cells.

FAQs

Q1: Do the laws of reflection apply to curved mirrors?
Yes, they apply to every point on the surface of a curved mirror. The normal at each point determines the angles of incidence and reflection.

Q2: Why is reflection important in daily life?
Without reflection, we wouldn’t see objects. It is the basis for mirrors, periscopes, telescopes, and even road safety devices.

Q3: What is lateral inversion?
In a plane mirror, the left side of the object appears as the right side in the image. This effect is called lateral inversion.

Q4: Can reflection happen without a mirror?
Yes, any surface, smooth or rough, reflects light. For example, walls, books, or even human skin reflect some amount of light.

Q5: Does reflection always produce an image?
No, only regular reflection produces a clear image (like mirrors or calm water). Irregular reflection makes objects visible but does not form a sharp image.

References

1. Lekner, J. (2016). Theory of reflection. Springer Series on Atomic, Optical, and Plasma Physics, 87.
2. Beeson, S., Mayer, J.W. (2008). The Reflection of Light. In: Patterns of Light. Springer, New York, NY
3. Halliday, D., Resnick, R. and Walker, J. (2014) Fundamental of Physics. 10th Edition, Wiley and Sons, New York.
4. https://byjus.com/physics/laws-of-reflection/#law-of-reflection-formula
5. Hecht, Eugene. (2002). Optics (4th ed.). San Francisco: Addison Wesley.
6. https://www.physicsclassroom.com/class/refln/lesson-1/the-law-of-reflection