Activity 12 Lec & Activity 9 | Convex Mirror

Images Formed in Convex Mirror

Activity 11 Lec & Activity 8 Lab | Plane and Concave Mirror

Images Formed in Plane and Concave Mirrors

Activity 7 Lab | Demonstration of Reflection of Light

The Law of Reflection states that "when a ray of light reflects off a surface, the angle of incidence is equal to the angle of reflection."

Source: https://bit.ly/2GZ0Wo3

To further demonstrate the reflection of light (laser light is unavailable), kindly click this link https://bit.ly/35mVvHJ.

      We can see different things because of the reflection of light. The highlighter showed in the picture above is an example of a nonluminous object. Nonluminous objects are dependent on luminous objects or the source of light. We cannot see them if there is no source of light such as the sun, bulbs, and other objects that emits light by itself. Reflection of light refers to the change in direction of light or bouncing of light from some surface. The light coming from the source strikes the object and bounces off from its surface. When the light reaches our eyes that's when we see the image. 

Mirror Reflection

    When a ray of light falls on any object (polished, smooth, shiny object), light from the object bounces back those rays of light to our eyes, and this phenomenon is known as “Reflection” or “Reflection of Light”. A mirror is a shiny, polished object (glass) which reflects most of the rays of light falling upon it.

Activity 10 Lec | Reflection of Light

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1. Can we see things around us without light?

  No. We can only see things, specifically nonluminous things, if there is light present. Nonluminous things depend on luminous things like light bulbs, the sun, and stars.

2. How do we see things around us?

     We see things around us by the reflection of light. The light emitted from luminous things reflected or bounced on the surface of nonluminous things.

3. What is reflection of light?

   Reflection of light refers to the change in direction of light or bouncing of light from some surface. The light coming from the source strikes the object and bounces off from its surface. When the light reaches our eyes that's when we see the image. The object formed in mirrors is also caused by the reflection of light. The light from the source is incident on the object facing the mirror. It gets reflected and the reflected light strikes the mirror. This light is reflected and reaches our eyes. 

4. What do you mean by the law of reflection?

     The Law of reflection states that when are a ray of light reflects off a surface, the angle of incidence is equal to the angle of reflection.

 

Activity 6 Lab | Marshmallow to Measure the Speed of Light

How Possible that the Speed of Light can be Measured by the Use of Marshmallows?

      We can measure the speed of light by melting the marshmallow inside a microwave oven. To operate, microwave ovens use the microwave which speed is the same as the speed of light as they are both EM waves. To get the speed, we need to have wavelength and frequency multiplied.  

     In this tasty setup, we can get the wavelength from the pattern created by the melted portion of the marshmallows. To achieve this, do not forget to turn off the rotating table as this would indicate the portion hit by the microwave energy. Note that it is only half so we need to multiply it by 2. After measuring the wavelength, look for the frequency indicated by the microwave oven model using the two data, we can then proceed to multiply and get the result which is the speed of light.

Activity 9 Lec | The History of the Speed of Light

      Light travels fast. It can travel 300,000 km per second. This speed is fast enough to go around the world seven and a half times in just a second. 

    It was around 17th century when there were a number of views about the nature of light. There were several scientists like Pierre Gassendi and Rene Descartes, who explained the behavior of light. Below are the lists of scientists who contributed in determining the speed of light and how each was able to come up with these discoveries.

a.) Ole Rømer (1670)

       A Danish scientist who went to the observatory in Paris to observe the eclipses of Io,  one of Jupiter's moons. He discovered that the speed of light is finite by measuring the apparent changes in the revolution of Io. With this, he claimed that it took 22 minutes for the light to travel across the diameter of the Earth's orbit. If we know the diameter of the orbit, then we can get the speed of the light. However, it was unknown in his time so he was not able to work it.  He still presented his findings and as expected, many were skeptical about it.

b.) James Bradley (1727)

        An English scientist who also used astronomical methods, like Rømer, to determine the speed of light. In his studies, he examined the position of stars which is known as the concept of stellar aberration. He inferred that the light is traveling towards the earth but the earth is moving at the same time so we get a difference in where the star is supposed to be to where the star is seemed to be.  He was then able to determine the speed of light considering that the earth's speed has a particular value. He concluded that the speed of light is around 303,000 km per second.

c.) Hippolyte Louis Fizeau

       He used mirrors and cogwheel in his experiment to determine the speed of light. The half silver deer were served as the light source. The light would pass through the half-silvered mirror and the spinning cogwheel then strikes the other mirror. The light would return via the separation of the cog and then it would go off the side halves of the mirror. Because the cogwheel is spinning, the light would pass through the gap and get blocked by the time the light returns. He calculated the speed by considering multiplying the distance twice (reflected) divided time it takes which is also multiplied twice. He also considered the cog with exactly 720 teeth. He then concluded that the speed of light is 313,000 km per second. His experiment was the first wheel to determine the speed of light without using astronomical methods referred to as time of flight methodology. However, still, it was not accurate.

d.) Jean Bernard Léon Foucault

       He improved Fizeau's experiment by replacing the cogwheel with a rotating mirror and reducing the length of the path. As the mirror spins, the light travels down through the half-silvered mirror and reflects again at a different angle depending on the frequency of the speed. He determined the speed of light by considering the angle between the light source number of spins and path length. He calculated the speed of light to reach 298,000 km per second. 

       Among the four scientists mentioned above, it was Foucault's which is closer to the speed of light we have today.

Activity 7 Lec | Theories of Light

         

Is Light a Particle or a Wave?
        

        After a series of experiments through the long years, scientists believe that light can be a particle or a wave. Light behaves like a particle at times and like a wave at other times. This duality is revealed by quantum mechanics. This particle-like behavior of light is supported by the idea that it is made up of photons which can be explained through the photoelectric effect. It can also behave like a wave as it produces interference patterns which are believed only waves can do.