Physics: Refraction Vs Reflection




Introduction: Physics: Refraction Vs Reflection

This experiment demonstrates in a simple way the difference between the concepts of refraction and reflection. There will also be a brief scientific explanation of the concepts and applications to our daily lives.


  1. Glass Bowl
  2. Decorative jelly ball (Can be bought in supermarkets or flower shops)
  3. Water
  4. A printed image or text

Step 1: Reflection

Place the image or text on a table and then place the glass bowl on top of the image. Check that you can see the image clearly.

Step 2: Reflection - What Is Going On

We can see objects because light is reflected off them and reaches our eyes to form an image. In this case, because the glass bowl is filled with air, the light passes through the same medium and is not deflected.

Laws of Reflection
1. The first law of reflection states that the incident ray, the reflected ray and the normal line are coplanar. That is, they coexist in the same geometric plane;

2. The reflected angle is equal to the angle of incidence.

Step 3: Refraction

Now place the decorative jelly balls into the bowl and notice that the image that was clear until then is now completely imperceptible.

Step 4: Refraction - What Is Going On

Refraction of light is defined as the change in the speed of propagation as a consequence of the change in the medium of propagation. In other words, when a ray of light changes from one medium to another, with different refractive indices, it undergoes a deflection, approaching or moving away from the normal.

The decorative jelly balls are composed of 99% water which means that the light rays now have to pass through different medium and as such will deflect in all directions and form an image that is not perceptible. They produce the classic effect we all know when we put a straw or a pencil into a glass of water.

Step 5: And When You Add Water

When water is added to the glass bowl, the space between the decorative jelly balls that was filled with air is now filled with water and the light rays therefore pass through only one medium again, the phenomenon of reflection occurs again and it is possible to see the image clearly again.

Step 6: Everyday Examples

The phenomena of light refraction and refraction are present in many of our everyday applications, ranging from frosted glass to the stained glass windows of many cathedrals. And there is also the curiosity of the concept being used in the military environment, for example, stealth aircraft. Like the scheme of the images, where an example of a radar wave is given.

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    7 months ago

    Nice, simple depiction and explanation!


    7 months ago on Step 6

    Does a stealth aircraft really cause the radio waves to refract rather than reflect? Or is it more like they absorb most of the waves and cause reflections at different angles rather than straight back?

    Miguel Augusto
    Miguel Augusto

    Reply 7 months ago

    Hello, sorry for the late reply. Obviously, the technology behind stealth aircraft is based on various concepts, such as the types of materials, the properties of reflection, absorption and refraction of light. This is just one example of the application of the physical concept and the difference between the two physical concepts.