When the reflected rays are parallel to each other then what type of reflection takes place?

Our ability to see and make sense of the world with our eyes depends on the reflective properties of light. Without reflection, we would only see luminous objects like the sun, light bulbs, and computer screens.

The light rays that allow us to see non-luminous objects such as our hands, the floor, and the people around us are lit by light rays that travel from a light source to the object and then bounce off the object towards our eyes.

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The light rays that arrive at our eyes after reflecting off of an object behave predictably - consistent with the law of reflection. How we perceive that light is influenced by the characteristics of the object's surface.

One characteristic of a surface that influences what we see is the surface's roughness because there are two general types of reflection: specular and diffuse. The smoother the surface is, the more specular the reflection.

On a very smooth surface, lines normal to neighboring points along that surface are parallel to each other. Since the angle of reflection* depends on the orientation of the normal a the point the light ray hts, a set of parallel incident ray*s encountering a smooth surface reflect so that the angles of reflection are all the same. As a result, the reflected ray*s will retain the same organization present in the incident rays.

Since the reflected rays retain the organization of the incident rays, reflection off of smooth surfaces preserves the organization of the reflected light, allowing us to see images in mirrors.

Diffuse reflection* occurs on rough surfaces. In diffuse reflection, all of the reflected rays still behave in accordance with the law of reflection, but the roughness of the surface results in a variation of the normals along the surface. With this variation, normals at neighboring points are no longer parallel to each other. Since the angle of incidence depends on the normal line at the exact point a ray hits, the incident angles for a set of parallel rays will not be the same, and each reflected ray will have a different angle of reflection. In other words, the rays scatter.

The orientation of the normal lines at neighboring points along a surface differentiates specular from diffuse reflection. If the normal lines are parallel, reflection will be specular. If they are not parallel, reflection will be diffuse. Note this is roughness at the microscopic level. Diffuse reflection occurs on surfaces that are smooth to the touch, such as paper. Specular reflection* occurs on curved surfaces such as a funhouse mirror.

Specular reflection is beneficial. Without it, we would not have cameras or mirrors. However, diffuse reflection is central to our ability to see the world. Aside from the limited number of luminous objects, such as light bulbs and the sun, everything we see around us is visible because of diffuse reflection.

Test your understanding of the concepts covered with the specular vs diffuse reflection problem set.

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Reflection is when light bounces off an object. If the surface is smooth and shiny, like glass, water or polished metal, the light will reflect at the same angle as it hit the surface. This is called specular reflection.

Diffuse reflection is when light hits an object and reflects in lots of different directions. This happens when the surface is rough. Most of the things we see are because light from a source has reflected off it.

For example, if you look at a bird, light has reflected off that bird and travelled in nearly all directions. If some of that light enters your eyes, it hits the retina at the back of your eyes. An electrical signal is passed to your brain, and your brain interprets the signals as an image.

Specular reflection

The angle at which light hits a reflecting surface is called the angle of incidence, and the angle at which light bounces off a reflecting surface is called the angle of reflection

If you want to measure these angles, imagine a perfectly straight line at a right angle to the reflective surface (this imaginary line is called ‘normal’). If you measure the angle of incidence and the angle of reflection against the normal, the angle of incidence is exactly the same as the angle of reflection. With a flat mirror, it is easy to show that the angle of reflection is the same as the angle of incidence.

Water is also a reflective surface. When the water in a lake or sea is very still, the reflection of the landscape is perfect, because the reflecting surface is very flat. However, if there are ripples or waves in the water, the reflection becomes distorted. This is because the reflecting surface is no longer flat and may have humps and troughs caused by the wind.

It is possible to make mirrors that behave like humps or troughs, and because of the different way they reflect light, they can be very useful.

Concave mirrors

The inside curve of a spoon is an example of a concave mirror

Concave mirrors are used in certain types of astronomical telescopes called reflecting telescopes. The mirrors condense lots of light from faint sources in space onto a much smaller viewing area and allow the viewer to see far away objects and events in space that would be invisible to the naked eye.

Light rays travel towards the mirror in a straight line and are reflected inwards to meet at a point called the focal point.

Concave mirrors are useful for make-up mirrors because they can make things seem larger. This concave shape is also useful for car headlights and satellite dishes.

Convex mirrors

Convex mirrors curve outwards, like the outside of a balloon.

Parallel rays of light strike the mirror and are reflected outwards. If imaginary lines are traced back, they appear to come from a focal point behind the mirror.

Convex mirrors are useful for shop security and rear-view mirrors on vehicles because they give a wider field of vision.

Scattering of light

Some light is scattered in all directions when it hits very small particles such as gas molecules or much larger particles such as dust or droplets of water.

The amount of scattering depends on how big the particle is compared to the wavelength of light that is hitting it. Smaller wavelengths are scattered more.

“Why is the sky blue?” is a common question. Light from the sun is made of all the colours of the rainbow. As this light hits the particles of nitrogen and oxygen in our atmosphere, it is scattered in all directions. Blue light has a smaller wavelength than red light, so it is scattered much more than red light. When we look at the sky, we see all the places that the blue light has been scattered from.

This is similar to the question: “Why are sunsets red?” When the Sun appears lower in the sky, the light that reaches us has already travelled through a lot more of the atmosphere. This means that a lot of the blue light has been scattered out well before the light arrives at us, so the sky appears redder.

Clouds appear white because the water droplets are much larger than the wavelengths of light. For this situation, all wavelengths of light are equally scattered in all directions.

In Light and sight: true or false? students participate in an interactive or paper-based ‘true or false’ activity that highlights common alternative conceptions about light and sight.

In Investigating reflection students investigate specular and diffuse reflection by looking into a dark box and shining a torch at various objects, coloured paper and a mirror.

To model blue sky and a red sunset, try shining white light from a torch or a projector into a glass container of water with a few drops of milk in it. You should see a blue haze from the sides. If you look to the far end of the container, you should notice the light has a reddish hue.

Question 6 Exercise

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Solution:

Regular reflection

1. In regular reflection, the reflected rays are parallel to each other.

2. Regular reflection occurs from a nicely polished regular reflective surface.

Diffused reflection

1. In diffused reflection, the reflected rays are not parallel to each other.

2. It occurs from a diffused or irregular surface.

In diffused reflection, the surface is rough. Laws of reflection hold true. Due to irregularities on the surface, reflected rays scatter in different directions.

Video transcript

Hello friends, welcome to yet another lido homework session in today's class, we are going to be doing a science problem so let's begin with the question the question here is differentiate between regular and diffused reflection does diffuse reflection means that the failure of the loss of reflection so to this the question we have is two parts so let's begin with the first part of The question, the first part, is to differentiate regular and diffused reflection so I am differentiating regular and diffused reflection so this is regular diffusion this is regular reflection sorry regular reflection and this is a diffused Reflection so the first one in regular reflection is that in regular reflection reflected rays are parallel to each other so in regular reflection reflected ray rays are parallel to each other to each other [Music] whereas in diffused reflection the reflected rays are not parallel to each other so here reflected reflected rays are not parallel to each other to each other so in regular reflection reflected rays are parallel whereas diffused reflection reflected rays are not parallel to each other the second differentiation is that in regular reflection this reflection occurs from a polished Regularly reflected surface whereas in diffuse reflection the diffused reflection occurs from a diffused or irregular surfaces so let's write our answer the second point the second point this reflection this reflection occur from Nice from a nicely polished surface polished surface so this reflection occurs from a Nicely polished I can say nicely polished regular reflected surface Nicely polished regular reflected surface so regular reflection in regular reflect that the reflection occurs from a nicely polished regular reflected surface whereas in diffused reflection it occurs it occurs from a diffused from a diffused or irregular from a diffused or Irregular surface irregular a regular the surface so in diffused reflection reflection occurs from irregular or diffused surface whereas in regular reflection occurs from a polished surface so this is the first part of the question. I have finished doing the Differentiation now let's see what the second part of the question the second part of the question says does diffuse reflection mean failure? of the law of reflection so let's see what the answer is that in diffuse reflection the surface is rough so the law of reflection holds true. so let's write in diffused Reflection in diffused Reflection the surface the surface is rough the surface is rough so the law of so the law of reflection law of low of Reflection holds true and why due to due to irregularities due to irregularities on the surface of the surface due to irregularities on the surface the reflected the reflected ray scatter indifferent directions in different direction so in diffuse reflection since the The surface is rough the law of reflection is true and why due to irregularities on the surface the reflected ray scatters in different Directions and thereby the law of reflection will become true for diffused reflection so friends i hope you have understood the solution of this question if you have any doubts or queries, please comment below and if you like this video give it a big thumbs up. and for further such videos, please subscribe to this channel till then thank you all

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