Rectilinear Propagation Reflection of Light



The changes in the surface's nature can cause differences in the reflection of light. The rectilinear propagation takes place at the time in which the light travels in a straight line. In this method, no interference is there within the light's traveling route. The course of a light changes as it travels from one medium to another. The medium can be of different components such as air, water, as well as glass. The reflection of light and its nature is dependent on these factors.

What is Rectilinear Propagation Reflection of Light?

It is proven that light travels in a straight line if no such interferences and distractions are there. Just as the light comes to contact with any surface, it is reflected. The surface is polished and clear, resulting in specular reflection (Blanquet et al. 2020). In the case of an unpolished and rough surface, the reflection of light becomes a diffused reflection. An easy examination can be done to test the theory of rectilinear propagation. If one person is standing on a hilltop and tries to look at the surrounding place, the person is able to see all the things. The reason behind this is that no interference is there between the individual's eyes and the surrounding things (Goncharenko et al. 2020).

This very person can face difficulties in seeing the same things if the person comes down and tries to look straight. As a result of this experiment, it is proved that the light moves in a straight line if uninterrupted.

The experiment on a rubber tube

Required objects

A candle, any other sources of light, and a flexible rubber tube


Light the candle and place it on a plain surface. Take the rubber tube and try to look at the candle's flame through one of its ends. The person should note the observation at this level. After that, the rubber tube has to bend a little, and again the person has to look from one of its ends at the candle's flames.

Figure 1: Experiment on rubber tubes


Based on this experiment it is observed that when the person sees the flames with the straight tube it is very easy to see the flames. At the moment when the tubes bend, the person becomes unable to see the flame with the bent tubes (Emedolu et al. 2020). The bend rubber tube blocks the sight and therefore the person is unable to see the flames further. This proves that light moves in a rectilinear way and a straight line.

The experiment with cardboards

Required objects

Plain and clear surface, a candle, three cardboards, and a sharp object


The candle is lighted and placed on a clear surface. Three holes have to be made on each three cardboard. The cardboards need to be placed just at the same position in front of another cardboard so that the holes remain at the same line. The person here needs to place an eye on the hole of the last cardboard and tries to look at the candle's flame.

Figure 2: Experiment with cardboards


One can experiment with the help of three cardboards about the fact that light moves in a straight way. If the three cardboards are placed in the same line and the whales are also in the same line, the person can easily see the flames of the candle through the holes. This proves that the light from the candle goes in a straight line (Zhang et al. 2021). Just at that moment, if one of the three cardboards is moved a little the positions of the three holes changes. In this situation, the person is no anymore able to see the flames of the candle. This is an important and most reliable example of the fact that light moves on rectilinear propagation.

Real-life examples

In an underwater place, an object seems smaller which an important example of rectilinear propagation is. As the medium of light waves changes, the motion of the waves changes as well. An object, put into water changes its medium, and due to this, its appearance changes. Another example can be presented by putting a hand into a bucket of water (Lomukhin & Butukhanov, 2018). In the time when the hand is drowned from air to water, the medium changes, and as result, the hand seems smaller than real. Light travels at different speeds not only in different mediums but also in different densities. Dispersion of light is also integrally connected to the rectilinear propagation light.


The reflection of light comes from the base and source of light. In case of changes within the surface medium, the nature of reflection is found to differentiate. At the time when a light is blocked by a surface, the light reflects in its opposite direction. As an example, if a light is blocked by a mirror, the reflection is created in a specular reflective manner. If light falls on a rough surface the refection is created in a random and scattered manner. As an example, everyone can see their face in a mirror and smooth-surfaced objects rather than a non-smooth and rough surface.


Q1. What are the two most important effects of rectilinear propagation of light?

The formation of day and night with the formation of shadow is the two most important natural effects of rectilinear propagation of light. Besides that, the formation of a particular image with the help of a pinhole camera is also another effect of this.

Q2. In which form, the light reflects when hit on a sharp surface?

The light reflects on a straight line and in a specular reflection mode when hit on a sharp surface. Reflection of light bounce in a straight line is a result of this.

Q3. What does the term 'interference' mean?

The term interference means two waves, forming a resultant wave in higher, lower, and most importantly on the same amplitude. This is a significant phenomenon in physics.

Q4. Which factors lead the light to bounce back in a scattered way?

The rough and unclear nature of a surface leads the light to bounce back in a scattered way. This is the basic nature of light.



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Emedolu, C. C., Ihejirika, C., & Nnamdi, B. S. (2020). Two Crucial Experiments on the Nature of Light: Beyond the Bounds of Wave-Particle Duality. AFRREV IJAH: An International Journal of Arts and Humanities, 9(1), 130-139. Retrieved on 10th June 2022 from:

Goncharenko, T., Yermakova-Cherchenko, N., & Anedchenko, Y. (2020). Experience in the Use of Mobile Technologies as a Physics Learning Method. In ICTERI Workshops (pp. 1298-1313). Retrieved on 10th June 2022 from:

Lomukhin, Y. L., & Butukhanov, V. P. (2018). Investigation of backward reflection from aqueous media at arbitrary grazing angles. Russian Physics Journal, 60(11), 1917-1923. Retrieved on 10th June 2022 from:

Zhang, X., Zhang, A., Sun, J., Zhu, X., Guo, Y. E., Qian, F., & Mao, Z. M. (2021, October). EMP: edge-assisted multi-vehicle perception. In Proceedings of the 27th Annual International Conference on Mobile Computing and Networking (pp. 545-558). Retrieved on 10th June 2022 from:


Thefactfactor (2022). Photometry and Sorcs of light. Retrieved from: [Retrieved on: 10th June 2022]

Updated on 13-Oct-2022 11:19:47