Laws of Reflection

Edited By Team Careers360 | Updated on Jul 02, 2025 04:31 PM IST

Have you ever noticed when you look at the mirror and see your face as clear as a picture? This is because the process of reflection takes place. For example, when light falls on a mirror, it reflects from it as it can penetrate it. This bouncing back of light is called reflection. Reflection in Physics is also applied in many things seen in daily life such as cameras, periscopes, or in viewing how light or sound functions. Let's explore the concept of reflection in detail.

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This Story also Contains

What is Reflection?
Laws of Reflection
Types of Reflection
Application of Reflection
Solved Examples on Reflection

Laws of Reflection - Definition, Diagram, Examples, FAQs

What is Reflection?

The phenomenon when a ray of light strikes an opaque surface, it bounces back instead of passing through it is called reflection. We can see objects and images in mirrors or on reflective surfaces with the help of reflection.

reflection diagram

There are two laws of reflection that help to describe how light reflects off surfaces. These laws are:

The Angle of Incidence Equals the Angle of Reflection: It states that the angle at which the ray strikes is equal to the angle at which it reflects. Mathematically it is represented as:

$θ_{i} = θ_{r}$

The Incident Ray, the Reflected Ray, and the Normal Lie in the Same Plane: The striking ray ( incident ray), the ray that is bouncing off the surface (reflected ray) and the perpendicular to the surface all lie in the same plane.

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Types of Reflection

Regular (Specular) Reflection
Irregular (Diffuse) reflection

Regular (Specular) Reflection: Regular Reflection occurs when light falls on a smooth surface and as a result, it creates a clear, and sharp image. The reflected rays are parallel to each other.

This smooth surface can be a mirror. A mirror is made of glass coated with a reflective material. This reflective material helps in reflecting light incident on it uniformly.

Example: Reflection in a plane mirror.

Irregular (Diffuse) reflection: When light falls on an uneven surface, it scatters in different directions, and as a result, no clear image is formed. This type of reflection is called Irregular reflection. This uneven surface can occur due to scratches, wear and tear, dirt on the surface, or due to the material of the surface.

The difference between regular and irregular reflection

S. No.	Regular Reflection	Irregular Reflection
1	When all reflected rays from a smooth surface are parallel to incident rays.	This is when incident parallel rays do not remain parallel to each other, the reflected rays do.
2	Smooth surfaces, such as mirrors, silver spoons, etc. provide this texture.	Rusty surfaces such as wood, doors, tables, books, etc. provide this texture.

Related Topics

Application of Reflection

Periscopes use reflection to observe advancing enemies on the battlefield from a safe distance.
We see objects because of reflections.
Mirrors with concave and convex lens surfaces can reflect a variety of different images.
Medical diagnostics rely on reflection, as does optical path 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.

Solved Examples on Reflection

Q1. An incident ray of light strikes a plane mirror at an angle of $30^{\circ}$ with the mirror surface. Approximately what angle will the reflection be?

Solution:

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 $= 600$

The angle of reflection

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.

Solution:

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,

$i + r + i^{'} + r^{'} = 180^{\circ}$

As a result of the law of reflection, $i = r$ and $r^{'} = i^{'}$
Substitute to obtain

$\begin{aligned} i + i + i^{'} + i^{'} = 180^{\circ} \\ i + i^{'} = 90 \end{aligned}$
In triangle $A O B$ , we have

$\begin{aligned} α + (90 - r) + (90 - i^{'}) = 180^{\circ} \\ α = r + i^{'} = i + i^{'} = 90^{\circ} \end{aligned}$
If $α = 90^{\circ}$ , the downward ray passes through $A$ and the upward ray passes through $B$ .

Frequently Asked Questions (FAQs)

1. Give two uses of reflection?

Periscopes use reflection to observe advancing enemies on the battlefield from a safe distance.
We see objects because of reflections.

2. What is total internal reflection?

The light is reflected back into the denser medium when it passes from a denser medium to a lighter medium at an angle greater than the critical angle for refraction. Total Internal Reflection refers to this phenomenon.

3. What are concave mirrors?

Objects beyond the focus of a concave mirror give real, inverted images. Objects within the focal range of a concave mirror give a virtual, erect, enlarged image.

4. How does light reflect?

It is known as the reflection of light when light rays hit the surface and bounce back.

5. Reflection law: What does it mean?

A smooth surface is defined as having an angle equal to that of the reflected ray on reflection. The angle is equal to the angle between the incident and reflected rays that is parallel to the line perpendicular to the surface at the point of contact.

6. What is the normal line in the context of reflection?

The normal line is an imaginary line perpendicular to the reflecting surface at the point where the light ray strikes. It's crucial in describing reflection because both the incident and reflected rays make equal angles with this normal line. Understanding the normal helps in accurately predicting the path of reflected light.

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

A plane mirror perfectly demonstrates the law of reflection. When light hits the mirror's surface, it bounces off at the same angle it arrived, creating a symmetrical reflection. This is why objects in a mirror appear to be the same distance behind the mirror as they are in front of it.

8. How does the law of reflection relate to the formation of images in mirrors?

The law of reflection is crucial for image formation in mirrors. It determines how light rays from an object are redirected by the mirror to form an image. In a plane mirror, the law ensures that the image is virtual, upright, and the same size as the object. In curved mirrors, it helps explain why images can be magnified, reduced, or inverted.

9. Can you explain how a solar cooker works using the law of reflection?

A solar cooker uses the law of reflection to concentrate sunlight for cooking. It typically has a parabolic reflective surface. When sunlight hits this surface, it reflects according to the law of reflection. The parabolic shape is designed so that all reflected rays converge at a single focal point, where the cooking pot is placed. This concentrates the sun's energy, generating high temperatures for cooking.

10. Why do flat mirrors produce virtual images while concave mirrors can produce real images?

This difference is due to how the law of reflection applies to these surfaces. In a flat mirror, reflected rays diverge after reflection, appearing to come from behind the mirror, creating a virtual image. In concave mirrors, the curved surface causes reflected rays to converge at a point in front of the mirror (for objects beyond the focal point), creating a real image that can be projected onto a screen.

11. Is there any situation where the law of reflection doesn't apply?

The law of reflection always applies to smooth surfaces on a macroscopic level. However, at very small scales or in certain quantum mechanical scenarios, light can behave differently. For instance, in the phenomenon of total internal reflection, light doesn't reflect off the surface but rather reflects within the medium it's traveling through.

12. How does the law of reflection relate to the concept of specular reflection?

Specular reflection is a direct application of the law of reflection. It occurs when light rays reflect off a smooth surface in an organized manner, with the angle of reflection equal to the angle of incidence for each ray. This type of reflection produces clear, mirror-like images and is the ideal demonstration of the law of reflection.

13. Can you explain how a periscope works using the law of reflection?

A periscope uses the law of reflection to redirect light and allow viewing around obstacles. It typically consists of two mirrors set at 45-degree angles to the periscope's axis. Light enters the top, reflects off the first mirror at a 90-degree angle (45° + 45°), travels down the periscope, and reflects off the second mirror, again at a 90-degree angle, towards the viewer's eye. This arrangement preserves the image while changing its direction.

14. What is the relationship between the law of reflection and Fermat's principle?

Fermat's principle states that light travels between two points along the path that takes the least time. The law of reflection can be derived from this principle. When light reflects off a surface, the path that takes the least time is the one where the angle of incidence equals the angle of reflection, which is exactly what the law of reflection states.

15. How does the law of reflection apply to concave mirrors?

In concave mirrors, the law of reflection applies at each point on the curved surface. The normal line at any point is perpendicular to the tangent plane at that point on the curved surface. This causes parallel incoming rays to converge at a focal point after reflection, explaining why concave mirrors can focus light and form real images.

16. What is the law of reflection?

The law of reflection states that when light reflects off a smooth surface, the angle of incidence is equal to the angle of reflection. This means the incoming light ray and the reflected light ray make the same angle with respect to the normal line (perpendicular) to the surface at the point of reflection.

17. How does the law of reflection contribute to the formation of mirages?

Mirages are optical illusions caused by the refraction of light, but the law of reflection plays a role in their appearance. In a hot road mirage, for instance, light from the sky is totally internally reflected off a layer of hot air near the ground. This reflection, following the law of reflection, creates the illusion of water on the road, which is actually a reflected image of the sky.

18. How does the law of reflection relate to the concept of retroreflection?

Retroreflection is a special case that utilizes the law of reflection multiple times. In retroreflective materials (like those used in road signs), light enters a tiny glass bead or corner cube and undergoes multiple internal reflections, each following the law of reflection. The cumulative effect is that light is sent back in the direction it came from, regardless of the angle of incidence.

19. What role does the law of reflection play in fiber optics?

In fiber optics, the law of reflection is crucial for total internal reflection, which keeps light confined within the fiber. When light hits the boundary between the core and cladding of the fiber at an angle greater than the critical angle, it reflects completely back into the core. This process, repeating along the length of the fiber, allows light to travel long distances with minimal loss.

20. How does the law of reflection explain the formation of rainbows?

Rainbows primarily form due to refraction and internal reflection in water droplets. The law of reflection plays a crucial role in the internal reflection part. After light enters a raindrop and is refracted, it reflects off the back of the droplet according to the law of reflection. This reflection, combined with further refraction as the light exits the droplet, separates the colors and creates the rainbow effect.

21. Why does a rough surface not produce a clear reflection like a smooth surface?

Rough surfaces don't produce clear reflections because they have many tiny, irregularly angled surfaces. Each of these microscopic surfaces reflects light according to the law of reflection, but in different directions. This scattering of light in multiple directions is called diffuse reflection, resulting in a less focused, unclear reflection.

22. How does the law of reflection explain why we can see ourselves in a mirror but not in a wall?

The law of reflection explains this difference. A mirror has a smooth surface that reflects light rays in a very organized manner, maintaining the relationship between incoming and outgoing rays. This preserves the image information. A wall, being rough, scatters light in all directions (diffuse reflection), disrupting the organized reflection needed for image formation.

23. How does the law of reflection contribute to the glare we see on water surfaces?

Glare on water surfaces is a direct result of the law of reflection. When sunlight hits a smooth water surface, it reflects according to the law of reflection. At certain angles, this reflected light can be intense and directed towards our eyes, causing glare. Ripples on the water create multiple reflecting surfaces, each following the law of reflection, spreading the glare over a larger area.

24. How does the law of 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, like those seen at the bottom of a swimming pool, the law of reflection applies to each point on the water's rippled surface. The cumulative effect of these reflections concentrates light into bright curves and patterns.

25. How does the law of reflection contribute to the design of solar panels?

While solar panels primarily work through absorption, the law of reflection is considered in their design to maximize efficiency. Anti-reflective coatings are often used to minimize reflection and increase absorption. In some designs, reflective surfaces are strategically placed to redirect light that would otherwise miss the panel, using the law of reflection to increase the amount of light captured.

26. Can the law of reflection be applied to other types of waves besides light?

Yes, the law of reflection applies to all types of waves, not just light. Sound waves, water waves, and even seismic waves follow the same principle when they encounter a boundary between two mediums. This universality makes the law of reflection a fundamental concept in wave physics.

27. How does the law of reflection explain why a pool appears shallower than it actually is?

While this phenomenon primarily involves refraction, the law of reflection contributes to the illusion. Light rays from the bottom of the pool reflect off the water's surface back into the pool when they hit at angles greater than the critical angle. This internal reflection, combined with refraction of the transmitted light, creates the illusion of a shallower pool.

28. What is the relationship between the law of reflection and polarization of light?

While the law of reflection itself doesn't cause polarization, it can affect polarized light. When unpolarized light reflects off a surface, the reflected light can become partially polarized, with the degree of polarization depending on the angle of incidence. At a specific angle (Brewster's angle), the reflected light can become completely polarized perpendicular to the plane of incidence.

29. How does the law of reflection explain why a pencil half-submerged in water appears bent?

While this phenomenon is primarily due to refraction, the law of reflection contributes to the complete image we see. The part of the pencil above water is seen directly, with some light reflecting off the water surface according to the law of reflection. The submerged part is seen due to refraction, but some light from this part also reflects off the bottom of the container, again following the law of reflection. The combination of these effects creates the illusion of a bent pencil.

30. Can you explain how a lighthouse uses the law of reflection?

Lighthouses use the law of reflection to project a powerful beam of light over long distances. The light source is placed at the focal point of a parabolic reflector. When light from this source hits the reflector, it follows the law of reflection at each point, resulting in a parallel beam of light that can travel far without significant spreading.

31. How does the law of reflection explain why we can see ourselves in a spoon?

The curved surface of a spoon acts like a combination of concave and convex mirrors. On the inside (concave) surface, the law of reflection causes light rays to converge, creating an upside-down image when you're far from the spoon and a magnified, right-side-up image when you're close. On the outside (convex) surface, the law of reflection causes light rays to diverge, creating a smaller, upright image.

32. Can you explain how a cat's eye reflector works using the law of reflection?

A cat's eye reflector uses the law of reflection in a clever way. It consists of a spherical reflector with a glass or plastic cover. Light entering the reflector bounces off the back surface and is reflected back in the direction it came from, regardless of the angle of incidence. This is achieved through multiple reflections, each following the law of reflection, making these reflectors visible from various angles.

33. Can you explain how a kaleidoscope works using the law of reflection?

A kaleidoscope uses multiple reflections, each following the law of reflection, to create symmetrical patterns. It typically contains three mirrors arranged in a triangle. Small objects at one end reflect multiple times off these mirrors. Each reflection obeys the law of reflection, creating a symmetrical image. As the objects move, the reflections change, creating ever-changing patterns.

34. What role does the law of reflection play in the phenomenon of light pillars?

Light pillars are optical phenomena where a vertical beam of light appears to extend above or below a light source. They're caused by the reflection of light from ice crystals suspended in the air. Each ice crystal acts like a tiny mirror, reflecting light according to the law of reflection. When many crystals are aligned horizontally, their collective reflections create the illusion of a pillar of light.

35. How does the law of reflection explain why a mirrored disco ball creates scattered light spots?

A disco ball is covered in small, flat mirrors. Each of these mirrors reflects light according to the law of reflection. As the ball rotates, each mirror reflects light in a different direction, but always following the law of reflection. This creates moving spots of light around the room, with each spot representing a reflection from one of the small mirrors on the ball.

36. Can you explain how a corner reflector works using the law of reflection?

A corner reflector consists of three mutually perpendicular reflective surfaces forming a corner. When light enters this corner, it undergoes three reflections, one off each surface. Each reflection follows the law of reflection. The cumulative effect of these three reflections is that light is always sent back in the direction it came from, regardless of the angle at which it entered the corner reflector.

37. How does the law of reflection contribute to the formation of a mirage in a desert?

In a desert mirage, the law of reflection plays a crucial role in the final stage of the illusion. As light from the sky travels through layers of air with different temperatures, it bends (refracts). When it reaches a layer where it would bend more than 90 degrees, it instead undergoes total internal reflection, following the law of reflection. This reflected light reaches our eyes, creating the illusion of water on the ground, which is actually a reflected image of the sky.

38. What is the relationship between the law of reflection and the principle of reversibility of light?

The principle of reversibility of light states that light can follow the same path backwards as it does forwards. This principle is a direct consequence of the law of reflection. If you reverse the direction of a reflected ray, it will follow the same path back to the source, reflecting off the surface at the same angle. This reversibility is why you can see your eye in a mirror looking at the reflection of your eye.

39. Can you explain how a retroreflective road sign works using the law of reflection?

Retroreflective road signs use tiny glass beads or prismatic reflectors. When light from a car's headlights hits these, it undergoes multiple internal reflections, each following the law of reflection. The shape and arrangement of these reflectors ensure that after these multiple reflections, the light is sent back in the direction it came from. This makes the sign appear bright to the driver, regardless of the angle at which the light hit the sign.

40. How does the law of reflection contribute to the sparkle of a diamond?

The sparkle of a diamond is due to its high refractive index and its cut, which creates many angled surfaces. When light enters the diamond, it undergoes multiple internal reflections, each following the law of reflection. The angles of the cut are designed so that much of this light is reflected back towards the viewer. The multiple reflections also separate the light into its component colors, creating the characteristic sparkle and fire of a well-cut diamond.

41. What role does the law of reflection play in the formation of glory (optical phenomenon)?

A glory is a circular rainbow-like optical phenomenon seen around the shadow of an observer's head. While it primarily involves diffraction and interference, the law of reflection plays a role. Light reflects off the back of water droplets in clouds, following the law of reflection. This reflected light then undergoes interference and diffraction to create the colored rings of the glory.

42. How does the law of reflection explain why a mirror image is reversed left to right but not top to bottom?

This is a common misconception. The mirror image isn't actually reversed left to right; it's reversed front to back. The law of reflection ensures that each point on an object reflects to a corresponding point that's the same distance behind the mirror. This creates a front-to-back reversal, which we interpret as left-to-right because we mentally rotate the image to face us. The top-to-bottom orientation remains unchanged because the vertical axis isn't affected by this front-to-back reversal.

43. Can you explain how a solar furnace works using the law of reflection?

A solar furnace uses a large array of mirrors (heliostats) to concentrate sunlight onto a single point. Each mirror is angled to reflect sunlight towards a central collector, following the law of reflection. The collector, often a parabolic dish, further concentrates this light to a focal point where temperatures can reach several thousand degrees Celsius. The precise positioning of each mirror, guided by the law of reflection, is crucial for focusing the maximum amount of sunlight.

44. How does the law of reflection contribute to the phenomenon of light scattering in the atmosphere?

While scattering is primarily a different phenomenon from reflection, the law of reflection plays a role in some aspects of atmospheric scattering. When light hits particles in the atmosphere larger than the wavelength of light, it can undergo reflection. Each of these reflections follows the law of reflection. The cumulative effect of many such reflections from different particles contributes to the overall scattering of light in the atmosphere.

45. What is the relationship between the law of reflection and the formation of caustics in photography?

Caustics in photography are bright patterns caused by light reflecting or refracting off curved surfaces. In reflection caustics, like those seen on the bottom of a pool, each point