Project: Light

At the seeing of a color-changing puddle on the street, interesting ideas about light struck into my mind

In theory, when a light ray encounters a surface, one or more of the following three things occur, the light ray:

Reflects off the surface and travels off in a different direction.
Passes from one medium into the other and continue on a new, straight line path.
Is absorbed

(as quoted from https://scienceprimer.com/reflection-refraction)

Reflection and Refraction

Reflection: Light bounces off an object and change the way -> The object’s surface should be solid and smooth enough

Source: http://electron6.phys.utk.edu/optics421/modules/m1/reflection_and_refraction.htm

Source: https://en.wikipedia.org/wiki/Reflection_(physics)

$Image result for light reflection and refraction$

Source: https://www.pinterest.com/pin/41236152812520504/?lp=true

Observation: mirror, metal (spoon), screen (TV, phone), eye retina

Refraction: Light still goes through the object but would be bent and change the way -> The object’s liquid

$refraction marching at angle$

Source: https://www.mathsisfun.com/physics/refraction.html

Observation: lenses, magnifying glasses, prisms, rainbows, eye cornea and lens

Experiments:

Simulation: Use a round object, i.e a ball, then:

– hit it into the wall -> Light particles meet the solid surface
– hit it into something soft like cloth -> Light particles meet the soft surface

Water is like a natural special mirror that both reflects and refract light.

The chameleon puddle

Use pieces of paper with different color and put them over a water puddle, so that the puddle looks like a color-changing screen.

Removing all objects possibly reflected into the puddle, it has no color at all.

Through the deep dark sea

Source: https://www.exploratorium.edu/snacks/critical-angle

Direct the light beam upward through the water so that it hits the surface of the water from underneath. You can shine the beam into the water through the transparent bottom of the aquarium, or in through a side wall. The beam will be more visible if you can dim the room lights.

Point the beam so that it hits the surface of the water at just about a right angle. In the aquarium, you may be able to see both the reflected beam, which bounces back into the water, and the refracted beam, which comes out of the water and into the air. (You can also search for the beam and track it with a piece of paper.)

Slowly change the angle at which the beam of light hits the surface of the water.

Notice that the beam reflected into the water grows brighter as the beam transmitted into the air becomes dimmer.

Experiment until you find the angle at which the transmitted beam completely disappears. At this angle, called the critical angle, all the light is reflected back into the water.

The invisible bottle

Preparation:
– 1 small glass bottle
– 1 clear glass
– a little vegetable oil or animal fat

Instruction:
Fill 1/3 of the glass with oil
Fill of the bottle with oil
Gently put the bottle inside the glass

Observation:
Part of the bottle which is inside the glass disappears

Explanation:
Light is transmitted through oil at a pace that is nearly the same as through glass

The moving arrows

Source: https://www.whatdowedoallday.com/water-refraction-science-experiment/

Preparation:
– Water
– Jar or glass
– A paper with a design on it. If you wish, you can download and print our printable. It is two pages and includes the colored bars and two arrows

$Materials for water refraction experiment.$

Instruction:
Place a jar or glass about 6 inches in front of the colored bars or arrows. Pour in the water. Keep the eyes on the bars/arrows as you slowly pour the water into the jar.

Exploration:
– Does it make a difference how close the water is to the paper?
– Does it make a difference if the jar is square or round?
– What about the size of the jar or glass?

Explanation:
Refraction is the bending of light. In this case, light traveled from the air, through the front of the glass jar, through the water, through the back of the glass jar, and then back through the air, before hitting the picture. Whenever light passes from one medium into another, it refracts.

In addition, the water acts as a magnifying glass, which bends the light toward the center. The light comes together at the focal point and beyond the focal point the image looks reversed because the light that was on the right is now on the left, and vice versa. Clear as mud?

The rainbow cup

Preparation:
– 2 paper cups
– tape
– scissors

Instruction:
Cut through the bottom of 1 cup with a small square-shape at the middle of the cup then seal the square with tape.
Create small holes at the bottom of the other cup with the tips of the scissors.
Seal the top of 2 cups together by tape.
Head the bottom with holes toward the light and watch through the square-hole at the other bottom

The rainbow on the wall

Source https://www.rookieparenting.com/make-your-own-rainbow-science-experiment/

Preparation:
– Water
– 1 clear glass
– 1 flashlight that emits strong focused white light. Flashlights that emit only yellowish light won’t work. Flashlights that don’t emit focused light also won’t work. Look for one with parabolic reflecting mirrors inside to focus the light, or one with a strong LED light
– 2 pieces of white cardboard

Instruction:
Place a jar or glass about 6 inches in front of the colored bars or arrows. Pour in the water. Keep the eyes on the bars/arrows as you slowly pour the water into the jar.

Instruction:
Fill the glass with water
Cut a narrow rectangle in the middle of one piece of paper
Stick that paper to the outside of the glass so that the slit is at the center

Place the other piece of paper on the floor on the other side of the glass to catch the rainbow
In a pitch dark room, point the flashlight at the slit
Start from the glass and slowly move the flashlight farther and farther from the glass
Adjust the distance and angle of the flashlight until you see a rainbow on the paper on the other side

Explanation:
When light passes from one medium to another medium of a different density (e.g. from air to water), the light bends.

How much a light is refracted depends on the wavelength of the light. The shorter the wavelength, the more it bends. Because lights of different colors have different wavelengths, each color is refracted by different amounts.

Therefore, white light is split up after passing from air to water and the individual colors become visible. This dispersion of light allows us to see the spectrum of colors that form a rainbow.

In nature, a rainbow is formed when sunlight is refracted on entering a droplet of water, reflected inside the back of the droplet and finally refracted again on leaving the droplet.

For more interesting experiement: