Reflection of Light - Definition, Properties, Types, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:34 PM IST

When you stand in front of the mirror you can see your own reflection, this phenomenon occurs because of the reflection of light. Reflection is an important phenomenon in Physics, as it is a key concept of many image-creating devices like Cameras, and telescopes. Let's discuss the reflection of light in detail.

This Story also Contains

What is Reflection of Light?
Laws of Reflection
Types of Reflection

Reflection of Light - Definition, Properties, Types, FAQs

What is Reflection of Light?

When a ray of light hits the surface, it bounces back from the surface. This bouncing back of light from the surface is called as Reflection of Light.

It is a fundamental concept in optics and necessary for creating images in devices like cameras, telescopes, and eyeglasses. Reflection of light follows the Law of reflection.

Laws of Reflection

The angle of incidence is equal to the angle of reflection: The angle formed by the incident ray with the normal is the same as the angle formed by the reflected ray with the same normal.

The Incident Ray, the Reflected Ray, and the Normal All Lie in the Same Plane: The reflected light, incident light (incoming light), and the normal line all lie in the same plane.

Let's understand the Law of Reflection by an example:

Consider a plane mirror XX'. Let MO be the light rays incident on the plane mirror at O. The ray MO is called the incident ray. The plane mirror reflects the incident ray along ON. The ray ON is called a reflected ray. Draw a line OP at O perpendicular to XX'. The line OP is called the normal.

Laws of reflection

The angle made by the incident ray with the normal is called the angle of incidence(i=angle MOP). The reflected ray ON makes an angle with the normal and this is called the angle of reflection. (r=angle PON). From the figure, you can observe that the angle of incidence is equal to the angle of reflection (i.e.∠r).

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Types of Reflection

The reflection is classified as follows:

Specular reflection
Diffused reflection
Multiple reflections

Specular Reflection

The mirror-like reflection of waves, such as light, from a surface, is known as specular reflection or regular reflection. Specular reflection reflects light from a single direction at the same angle. The diffraction of a plane wave on a flat boundary causes the reflection phenomena. The electromagnetic fields at the border oscillate exactly in phase only in the specular direction when the boundary size is significantly bigger than the wavelength. A mirror specifically designed for specular reflection is an example of specular reflection. Regular reflection, for example, causes a glare in the eyes, making an object less visible. Regular reflection is an example of sunlight reflected from a metallic car body, or silver or gold surfaces.

Specular reflection

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Diffused Reflection

When light reaches a material's surface, it reflects around in all directions due to the various reflections from microscopic imperfections inside the material and its rough surface. This is known as the diffused reflection. The actual shape of the reflection is determined by the material's structure. Lambertian reflectance is a prominent diffuse reflection model in which light is reflected with equal intensity or radiance in all directions, as specified by Lambert's cosine law. Most of the light we see comes from diffuse reflection from an object's surface. In contrast to specular reflection, diffuse reflection occurs when light is scattered in a variety of directions away from the surface. Diffuse reflection reflects light from a wide variety of directions. Diffuse reflection allows items to be seen.

Diffused reflection

Multiple Reflection

One vision arises when light reflects off a mirror. The appearance of an infinite number of images along a straight line is created by two mirrors aligned perfectly face to face. A circle is formed by the various images perceived between two mirrors that would be at an angle to each other. The virtual intersection of the mirrors is where the circle's center is placed. The appearance of an infinite number of pictures organized in a plane is created by a square of four mirrors set face to face. The numerous images seen between four mirrors forming a pyramid, each pair at an angle to the other, lie across a spherical surface. For instance, KALEIDOSCOPE is a lovely pattern created by many reflections. Periscopes take advantage of it. Submarines, battle tanks, and bunker soldiers all use periscopes to see items that aren't visible directly.

Total Internal Reflection

Total internal reflection is a phenomenon that occurs when light travels from the medium with a high refractive index to a low refractive index.

Optical fibers and mirages are examples of Total Internal Reflection.

Conditions to achieve the total internal reflection:

In order to achieve the total internal reflection, the following conditions must be met,

The light must pass through a denser medium to reach a rarer medium.
The angle of incidence inside the denser medium must be larger than the critical angle, for example, from water to air.

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Frequently Asked Questions (FAQs)

1. For normal incidence on a plane mirror surface, what are the values of the angle of incidence and angle of reflection?

The angle between the reflector and the light rays is 90° , when the light rays is incident conventionally on a plane mirror surface.

This indicates that the angle of incidence between the incident light rays and the normal is 0o.

Because the angle of incidence is 0 degrees, the angle of reflection is also 0o. (Due to the law of light reflection).

2. What is light?

Light is an electromagnetic wave that travels as a kind of energy. Light is a kind of energy. Light always travels as a straight line. The propagation of light does not necessitate the use of a medium. It can even travel through a vacuum or air.

3. Define incident and reflected rays?

The light rays incident on the plane mirror is called the incident ray. The plane mirror reflects the incident ray which is called reflected ray.

4. What is total internal friction?

The ray which is totally reflected back to the same medium is called the total internal reflection (r> 90o).

5. What are the types of reflection?

Specular reflection
Diffused reflection

6. How does a kaleidoscope create its patterns?

A kaleidoscope creates patterns through multiple reflections. It typically contains three mirrors arranged in a triangle, with small, colorful objects at one end. As you rotate the kaleidoscope, light reflects off the mirrors multiple times, creating symmetrical patterns from the objects.

7. What is a parabolic mirror and how does it reflect light?

A parabolic mirror has a curved surface in the shape of a parabola. It reflects all light rays parallel to its axis to a single focal point. Conversely, light emanating from the focal point is reflected as parallel rays. This property makes parabolic mirrors useful in telescopes and satellite dishes.

8. How do polarized sunglasses reduce glare?

Polarized sunglasses reduce glare by blocking horizontally polarized light. Glare often comes from light reflected off horizontal surfaces like water or roads, which tends to be horizontally polarized. The vertical polarization filter in the sunglasses blocks this reflected light, reducing glare.

9. What is the relationship between absorption and reflection?

Absorption and reflection are complementary processes. When light hits a surface, some of it is reflected and some is absorbed. The amount of each depends on the material's properties. A perfect reflector would reflect all light and absorb none, while a perfect absorber (like a black body) would absorb all light and reflect none.

10. How does the color of an object affect its reflectivity?

The color of an object is determined by which wavelengths of light it reflects and which it absorbs. A red object appears red because it reflects red light and absorbs other colors. White objects reflect all visible wavelengths, while black objects absorb most visible wavelengths.

11. How does the reflectivity of a surface change with the angle of incidence?

Generally, the reflectivity of a surface increases as the angle of incidence increases (measured from the normal). At very high angles of incidence (close to 90° from the normal), almost all light is reflected, even for materials that aren't typically very reflective.

12. What is the critical angle in total internal reflection?

The critical angle is the smallest angle of incidence at which total internal reflection occurs. It's the angle at which light traveling from a denser medium to a less dense medium refracts at 90° to the normal. Any angle of incidence larger than this will result in total internal reflection.

13. What is a corner reflector and how does it work?

A corner reflector consists of three mutually perpendicular reflective surfaces. When light enters this arrangement, it undergoes three reflections and exits parallel to its entry path, regardless of the angle of incidence. This property makes corner reflectors useful in surveying and navigation.

14. How do optical fibers use total internal reflection?

Optical fibers use total internal reflection to transmit light signals over long distances with minimal loss. The fiber consists of a core with a higher refractive index surrounded by a cladding with a lower refractive index. Light entering the fiber at the correct angle undergoes repeated total internal reflections, staying within the core.

15. How does the roughness of a surface affect reflection?

The roughness of a surface determines whether it produces specular or diffuse reflection. Smooth surfaces (roughness less than the wavelength of light) produce specular reflection. Rough surfaces (roughness greater than the wavelength of light) cause diffuse reflection.

16. How does a plane mirror form an image?

A plane mirror forms a virtual image by reflecting light rays from an object. The image appears to be behind the mirror, is the same size as the object, and is laterally inverted (left and right are switched). The distance of the image behind the mirror is equal to the distance of the object in front of it.

17. What's the difference between regular and diffuse reflection?

Regular reflection occurs on smooth surfaces, where parallel light rays reflect at the same angle, producing a clear image. Diffuse reflection happens on rough surfaces, where light rays scatter in different directions, resulting in no clear image formation.

18. Can light reflect off transparent surfaces?

Yes, light can reflect off transparent surfaces like glass or water. This is why you can sometimes see reflections in windows or on the surface of a lake. The amount of reflection depends on the angle at which light hits the surface and the refractive indices of the materials involved.

19. What is total internal reflection?

Total internal reflection occurs when light traveling in a denser medium tries to enter a less dense medium at an angle greater than the critical angle. Instead of refracting, all the light is reflected back into the denser medium. This principle is used in fiber optics and prisms.

20. How do retroreflectors work?

Retroreflectors are devices that reflect light back to its source regardless of the angle of incidence. They typically use corner reflectors or small glass beads. Retroreflectors are used in road signs, bicycle reflectors, and safety clothing to enhance visibility at night.

21. What is reflection of light?

Reflection of light is the phenomenon where light waves bounce off a surface and change direction. When light hits a smooth, reflective surface like a mirror, it bounces back in a predictable manner, following the law of reflection.

22. What is the law of reflection?

The law of reflection states that the angle of incidence is equal to the angle of reflection. In other words, when light hits a reflective surface, it bounces off at the same angle it arrived, but on the opposite side of the normal line (an imaginary line perpendicular to the surface).

23. What causes the glare from wet roads at night?

The glare from wet roads at night is caused by specular reflection. Water on the road creates a smooth surface that reflects light from car headlights directly into drivers' eyes, rather than scattering it as a dry, rough road surface would.

24. What is the difference between a real and virtual image?

A real image is formed when light rays actually converge at a point, and can be projected on a screen. A virtual image, on the other hand, is formed when light rays appear to diverge from a point, but don't actually pass through it. Virtual images cannot be projected on a screen.

25. How do car rear-view mirrors reduce glare at night?

Car rear-view mirrors often have a "day-night" setting. In the night position, the mirror is tilted slightly, so most of the light from bright headlights behind you is reflected towards the car's ceiling. You see a dimmer reflection from the silvered back of the glass, reducing glare.

26. What is the difference between specular and diffuse reflection?

Specular reflection occurs on smooth surfaces where light rays reflect at the same angle, producing a clear image (like a mirror). Diffuse reflection happens on rough surfaces where light scatters in many directions, producing no clear image (like a white wall).

27. What is the principle behind a one-way mirror?

A one-way mirror (or two-way mirror) is a piece of glass coated with a thin layer of metal. It allows some light to pass through and reflects the rest. When one side is brightly lit and the other is dark, people on the dark side can see through while those on the bright side see their reflection.

28. How do curved mirrors affect the reflection of light?

Curved mirrors change the direction of reflected light rays, either converging or diverging them. Concave mirrors (curved inward) can converge parallel light rays to a focal point, while convex mirrors (curved outward) diverge light rays, creating a wider field of view.

29. What is the difference between reflection and refraction?

Reflection is the bouncing back of light from a surface, where the light stays in the same medium. Refraction is the bending of light as it passes from one medium to another with a different refractive index. Both phenomena involve a change in the direction of light propagation.

30. How does the refractive index of a material relate to its reflectivity?

The refractive index of a material is related to its reflectivity. Materials with a higher refractive index tend to be more reflective. This relationship is described by Fresnel's equations, which show that the amount of light reflected at an interface increases as the difference in refractive indices between the two materials increases.

31. What is Brewster's angle?

Brewster's angle is the angle of incidence at which light with a particular polarization is perfectly transmitted through a transparent dielectric surface, with no reflection. At this angle, the reflected light is completely polarized perpendicular to the plane of incidence.

32. How do mirages form?

Mirages form due to the refraction of light in layers of air with different temperatures and densities. In hot conditions, the air near the ground is warmer and less dense than the air above. This causes light rays to bend upward, creating an illusion of a reflected image, often mistaken for water on a hot road.

33. What is the principle behind retroreflective materials used in road signs?

Retroreflective materials used in road signs contain tiny glass beads or prismatic reflectors. When light from car headlights hits these materials, it undergoes multiple reflections inside the beads or prisms and is sent back in the direction it came from, making the signs visible to drivers at night.

34. How does the reflectivity of water change with viewing angle?

The reflectivity of water increases as the viewing angle becomes more oblique (closer to parallel with the surface). This is why you can see clearer reflections on a lake when looking across it at a low angle, compared to looking straight down into the water.

35. What is coherent reflection?

Coherent reflection occurs when light waves reflect off a surface and remain in phase with each other. This happens with smooth, flat surfaces and results in specular reflection. Incoherent reflection, on the other hand, occurs when reflected waves are out of phase, resulting in diffuse reflection.

36. How do anti-reflective coatings work?

Anti-reflective coatings work by using destructive interference. A thin layer of material with a specific thickness and refractive index is applied to a surface. Light reflected from the top of this layer interferes destructively with light reflected from the underlying surface, reducing overall reflection.

37. What is the principle behind a solar cooker?

A solar cooker uses reflection to concentrate sunlight onto a cooking vessel. It typically employs a parabolic reflector to focus parallel sunlight rays onto a single point or a small area, generating high temperatures for cooking without using fuel.

38. How does reflection contribute to the formation of rainbows?

Rainbows form through a combination of reflection and refraction in water droplets. Sunlight enters a raindrop, refracts, reflects off the back of the drop, and then refracts again as it exits. This process separates white light into its component colors, creating the rainbow effect.

39. What is the difference between metallic and dielectric mirrors?

Metallic mirrors reflect light by free electrons in the metal surface, while dielectric mirrors use interference effects in multiple thin layers of dielectric materials. Dielectric mirrors can achieve higher reflectivity and can be designed for specific wavelengths, but are more complex and expensive to produce.

40. How does the principle of reflection apply in fiber optic communication?

In fiber optic communication, light signals travel through thin glass or plastic fibers by repeated total internal reflection. The core of the fiber has a higher refractive index than the cladding, ensuring that light entering at the correct angle remains trapped inside the core, allowing for long-distance transmission with minimal loss.

41. What is a retrograde reflection?

Retrograde reflection, also known as backscattering, occurs when light is reflected back towards its source, regardless of the angle of incidence. This phenomenon is utilized in retroreflectors, which are used in road signs, bicycle reflectors, and safety clothing to enhance visibility.

42. How do reflections contribute to the appearance of depth in still water?

Reflections in still water contribute to the appearance of depth by creating a mirror image of objects above the water surface. This symmetry provides visual cues that our brains interpret as depth. The slight differences between the real object and its reflection due to the water's surface also enhance this effect.

43. What is the principle behind a corner cube reflector?

A corner cube reflector consists of three mutually perpendicular reflective surfaces forming a corner. Light entering this arrangement undergoes three reflections and exits parallel to its entry path, regardless of the angle of incidence. This property makes corner cube reflectors useful in surveying, laser ranging, and space applications.

44. How does the albedo of a planet affect its temperature?

Albedo is a measure of a surface's reflectivity. Planets with higher albedo reflect more incoming solar radiation back into space, which tends to keep them cooler. Conversely, planets with lower albedo absorb more radiation, which can lead to higher surface temperatures.

45. What is the difference between specular and diffuse reflection in terms of energy distribution?

In specular reflection, the reflected energy is concentrated in a specific direction, resulting in a clear image. In diffuse reflection, the energy is scattered in many directions, resulting in no clear image formation. The total amount of reflected energy can be the same, but its distribution differs.

46. How does the principle of reflection apply to sound waves?

Sound waves reflect off surfaces in a manner similar to light waves, following the law of reflection. This is why you can hear echoes in large, empty rooms or canyons. The reflection of sound waves is also the basis for technologies like sonar and ultrasound imaging.

47. What is the role of reflection in the greenhouse effect?

Reflection plays a crucial role in the greenhouse effect. Sunlight passes through the atmosphere and warms the Earth's surface. The Earth then emits infrared radiation, some of which is reflected back to the surface by greenhouse gases in the atmosphere, leading to additional warming.

48. How do cats' eyes seem to glow in the dark?

Cats' eyes appear to glow in the dark due to a reflective layer called the tapetum lucidum behind their retinas. This layer reflects light that has passed through the retina back through it, giving the light a second chance to be detected and enhancing night vision. The reflected light is what we see as the "glow."

49. What is the principle behind a Fresnel reflector?

A Fresnel reflector is a type of concentrating solar power technology. It uses long, thin segments of mirrors to focus sunlight onto a fixed absorber located above the mirrors. The principle is similar to a parabolic reflector, but Fresnel reflectors are flatter and easier to manufacture and maintain.

50. How does the reflectivity of a surface change when it's wet?

When a surface becomes wet, its reflectivity generally increases. This is because the water forms a thin, smooth layer over the surface, creating more specular reflection. This is why wet roads often appear shinier and can produce more glare, especially at night.

51. What is the relationship between reflection and the color of objects?

The color we perceive an object to be is determined by which wavelengths of light it reflects and which it absorbs. For example, a red apple appears red because it reflects red light while absorbing most other colors. A white object reflects all visible wavelengths, while a black object absorbs most visible wavelengths.

52. How does reflection contribute to the formation of caustics?

Caustics are patterns of light formed when light rays are reflected or refracted by a curved surface. In reflection, caustics can be seen when light reflects off a curved, shiny surface like the inside of a coffee cup. The reflected light concentrates along certain lines or curves, creating bright patterns.

53. What is the principle behind a solar thermal power plant using mirrors?

Solar thermal power plants use large arrays of mirrors to concentrate sunlight onto a central receiver. These mirrors, often arranged in a parabolic shape, reflect and focus sunlight to heat a fluid (often molten salt) to high temperatures. This heat is then used to generate steam, which drives turbines to produce electricity.

54. How does the principle of reflection apply in radar technology?

Radar technology relies on the reflection of radio waves. The radar system sends out radio waves, which reflect off objects and return to the receiver. By analyzing the reflected waves, the system can determine the distance, speed, and direction of objects. This principle is similar to how bats use echolocation.

55. What is the difference between reflection and scattering of light?

Reflection involves light bouncing off a surface at a predictable angle, following the law of reflection. Scattering, on the other hand, occurs when light interacts with small particles or rough surfaces and is redirected in many directions. While reflection preserves the directionality of light, scattering tends to diffuse it.