A spectrum is a band of colours formed when white light is separated through refraction when passing through a prism.

 

Optical Illusions

Optical Illusions can use color, light and patterns to create images that can be deceptive or misleading to our brains. The information gathered by the eye is processed by the brain, creating a perception that in reality, does not match the true image. Perception refers to the interpretation of what we take in through our eyes. Optical illusions occur because our brain is trying to interpret what we see and make sense of the world around us. Optical illusions simply trick our brains into seeing things which may or may not be real.
Try out some of these illusions and discover just how tricky it can be for your brain to accurately interpret the images from your eyes.

How do we Change Colours?

Color from Light

The color of anything depends on the type of light sent to our eyes; light is necessary if we are to have any perception of color at all. An object is "colored," as stated above, because of the light it reflects—all other colors are absorbed into that specific object. So then, an apple appears red because it reflects red light. 

White light from the sun contains all the possible color variations. Yet, the human eye can only respond to certain colors and wavelengths, and not everyone sees the same colors or exact same shades of a color. We are capable of seeing color because our eyes have light and color-sensitive receptors.

These receptors are called rods (receptive to amounts of light) and cones (sensitive to colors). Being able to see color is a sensation, just like smelling a pie fresh out of the oven or tasting your favorite meal. Different foods smell and taste different to each person, and likewise, no color is seen exactly the same by two people, because each person's rods and cones vary.   

Color
The primary colors of light are red, blue, and green, and the secondary are yellow, cyan, and magenta. It is very important to know that mixing pigment and mixing light are very different. Red and green paint, for example, make brown paint, but red and green light make yellow light. When beams of light are mixed without any absorption, an additive process occurs. The more we mix the beams, the closer they get to being white light. However, when we put light through a color filter, a subtractive process occurs. Some wavelengths of light are being absorbed (subtracted) and we only see the wavelengths that are selectively given off.

Speed of Light

Speed of Light

The speed of light is the speed at which light travels in vacuum/empty space. Physicists often use the letter ‘c’ to denote the speed of light. It has the value 299,792,458 meters per second.  A photon travels at this speed in a vacuum.

According to special relativity, ‘c’ is the maximum speed at which all energy and matter in the universe can travel. It is the speed of all mass less particles such as photons —including electromagnetic radiation —in a vacuum. 

Spectrum Experiment

Experiment 1 – Creating a Spectrum

Aim

To see if white light can create a Spectrum with the help of a prism.

Hypothesis/Prediction

I predict that a white light will create a spectrum when the prism separates the light into 7 rays.

Materials Needed                             

• Prism
• Source of Light
• Screen

Procedure

Place the prism between the screen and the sunlight. Rotate the prism until you see a rainbow on the screen. 

Observation

There is a spectrum formed when the sunlight hits the prism.

Conclusion

A ray of white light will form a spectrum when it hits a prism.

How does Light Travel?

Light Moves in Waves

Light is a form of energy made of electromagnetic waves. The entire range of light is called the electromagnetic spectrum. The light you see is referred to as "visible light."

 

Usually, light travels very quickly. Light waves can travel up to 300,000 km per second. Light traveling from the sun takes about 8.5 minutes to reach the earth. Light waves can be large or small. How big those waves are determines what type and color of light it is. Some waves are so small they actually appear as straight lines. However, light only moves in straight lines when it is not passing through a medium.

Light Waves Can Pass through a Medium

Light waves can pass through air, water, glass, or other mediums. Passage through a medium can affect the speed and direction of the light waves. When it passes through a medium, such as water, it slows down. That is why a pencil will appear bent when placed in a glass of water.

 Only in spaces where there is no interference of its movement can light waves travel at maximum speed. When the waves are passing from the sun to the earth, the light is travelling as fast as it can go. This is faster than sound. When light waves pass through a dark, thick substance, such as a heavy cloth, the movement is slower. Some light waves may be absorbed by the medium. This is why not much light is reflected from the cloth when the waves bounce onto it.

 

 

Can light be bent?

Diffraction is a property of waves. Therefore light will always bend around corners. The reason you can’t see behind a wall when you can hear a sound behind the wall is because the wave length of light is so much smaller than that of sound.

The amount of diffraction depends heavily on the wavelength. The smaller the wavelength, the less it will ‘bend’ around a corner. And the bigger the wavelength, the more it will bend. Radio waves for example, have VERY large wavelengths, which is why your radio works inside the car or a building. To stop or prevent a wave from diffracting, you need an obstacle that is at least as big as the wavelength of the wave.