PHYSICAL SCIENCE FOR HIGHSCHOOL, Cheat Sheet of Earth science

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Physical Science (SHS)

2ND SEMESTER

QUARTER 4 – MODULE 5

VARIOUS LIGHT

PHENOMENA

I. Various light phenomena After your encounter with this module, you are expected to:

◆ CONTENT STANDARD: The learners demonstrate an understanding

of:

1. Light as a wave and particle.

◆ PERFORMANCE STANDARD: The learners shall be able to design and

create a useful product for practical purposes that uses mirror and lenses.

◆ LEARNING COMPETENCIES: The learners will: Explain various

phenomena such as

A. Your reflection on the concave and convex sides if a spoon looks

different

B. Mirages

C. Light form a red laser passes more easily though red cellophane

than green cellophane

D. Clothing of certain colors appear different in artificial light and in sulight

E. Haloes, sundogs , primary rainbows , secondary rainbows , and

supernumerary bows

F. Why clouds are usually white and rainclouds dark

G. Why the sky is blue and sunsets are reddish

II. CONCEPT NOTES

In an approximate way, light is both a particle and a wave. But in an exact representation, light is neither a particle nor a wave, but is something more complex. As a metaphor, consider a cylindrical can of beans. If you hold the can sideways, force a friend to only look at its shadow, and ask him what shape the object has, he will respond "rectangular". But now turn the can ninety degrees, have a second friend look at just the shadow, and he will tell you the can is "circular". Now have your two friends debate each other about the true shape and they will not make much progress. Which one is right? They are both right in away and both wrong in a way. A cylinder is circular as seen from one angle, and rectangular from another angle, but in reality it is much more than a circle plus a rectangle. It is something more complex: a three-dimensional shape that can't be fully described through two-dimensional shapes such as circles and rectangles. The problem is that your friends were looking at shadows of the can of beans

photon is a fluctuating probability distribution with quantized properties, it can do all these things in a completely sensible way. Amazingly, all quantum objects from electrons to protons behave as quantized probability distributions, and not just photons. If you find a quantum particle/wave hard to visualize, don't let this difficulty tempt you to dismiss quantum theory as nonsense. Quantum theory has been experimentally verified in hundreds of laboratories for almost a century now. Additionally, the semiconductor chip inside the computer you have in front of you right now crucially depends on quantum theory being right. To dismiss quantum theory as quackery because its concepts are hard to visualize is to say that computers don't exist. Reflection of light (and other forms of electromagnetic radiation) occurs when the waves encounter a surface or other boundary that does not absorb the energy of the radiation and bounces the waves away from the surface. The simplest example of visible light reflection is the surface of a smooth pool of water, where incident light is reflected in an orderly manner to produce a clear image of the scenery surrounding the pool. Throw a rock into the pool, and the water is perturbed to form waves, which disrupt the reflection by scattering the reflected light rays in all directions. When electromagnetic radiation, in the form of visible light, travels from one substance or medium into another, the light waves may undergo a phenomenon known as refraction, which is manifested by a bending or change in direction of the light. Refraction occurs as light passes from one medium to another only when there is a difference in the index of refraction between the two materials. The effects of refraction are responsible for a variety of familiar phenomena, such as the apparent bending of an object that is partially submerged in water and the mirages observed on a hot, sandy desert. The refraction of visible light is also an important characteristic of lenses that enables them to focus a beam of light onto a single point.

A. Your reflection on the concave and convex sides of a spoon looks

different This topic gives an overview of; Playing with

• Spherical Mirrors • Concave mirror • convex mirror Playing with Spherical Mirrors Pedro and Mario were waiting for their dinner. Mario lifted a stainless-steel plate and saw his image in it. Oh! This plate acts as a plane mirror. My image is erect and is of the same size. Pedro saw her image using the back of a steel spoon. Mario look here! I can also see my erect image though it is smaller in size. This spoon also acts as a mirror of some kind, said Pedro. You can also use a spoon or any curved shining surface to see your image. Activity 1

Take a stainless steel spoon. Bring the outer side of the spoon near your face and look into it. Questions: 1. Do you see your image in it. 2. Is this image different from what you see in a plane mirror? Is this image erect? 3. Is the size of the image the same, smaller or larger? Now look at your image using the inner side of the spoon. This time you may find that your image is erect and larger in size. If you increase the distance of the spoon from your face, you may see your image inverted. You can also compare the image of your pen or pencil instead of your face. The curved shining surface of a spoon acts as a mirror. The most common example of a curved mirror is a spherical mirror. If the reflecting surface of a spherical mirror is concave, it is called a concave mirror. If the reflecting surface is convex, then it is a convex mirror. The inner surface of a spoon acts like a concave mirror, while its outer surface acts like a convex mirror. We know that the image of an object formed by a plane mirror cannot be obtained on a screen. Let us investigate if it is also true for the image formed by a concave mirror. Convex mirror are curved outward like the bottom of a spoon When light rays hit the surface of a convex mirror , the light rays move away from each other. Your image appears smaller than you really are and is right side up. A concave mirror has a reflective surface that is curved inward and away from the light source. Concave mirrors reflect light inward to one focal point. Unlike convex mirrors, the image formed by a concave mirror shows different image types depending on the distance between the object and the mirror.

B.MIRAGE

Explain the Mirage Phenomenon on this diagram.

C. Light from a red laser passes more easily through red cellophane than green

cellophane.

White light If you shine torch light onto a sheet of paper, the light from the torch appears white. The light given out by torch lights, light globes and the Sun is white light. Some sources of light, for example colored neon lights or LEDs, do not produce white light, but colored light. If you want to know what color make-up or clothes will appear under normal circumstances, you need to check the colors in white light. Checking the colors under colored light can cause them to look very different.

The light spectrum If a beam of white light from a globe or from the Sun is shone through a triangular prism, a rainbow is produced. This is because the white light that comes from a light globe or from the Sun is a mixture of many different colors. When white light passes through a prism, it is split up into these separate colors White light is therefore a mixture of red, orange, yellow, green, blue and violet light. It is our eye that sees this mixture as 'white’. Activity 3: EXPERIEMNT Color Combinations You will need: Three flashlights Red, green, and blue pieces of cellophane Three rubber bands A sheet of white card What to do: In a well-lit room, hold a piece of red cellophane in front of your eyes.

1. What do you see?
2. What is the normal color of the objects that seem brightest when viewed through the cellophane?
3. What is the normal color of the things that seem darkest? Make the room as dark as possible and turn on a flashlight. Fix a blue piece of

Light from a laser is monochromatic, which means it only produces one colour. (Lasers are extremely dangerous and can cause permanent eye damage. Extreme care must be taken to ensure that light from a laser never enters someone’s eyes.) Colour of objects Objects appear different colours because they absorb some colours (wavelengths) and reflected or transmit other colours. The colours we see are the wavelengths that are reflected or transmitted. For example, a red shirt looks red because the dye molecules in the fabric have absorbed the wavelengths of light from the violet/blue end of the spectrum. Red light is the only light that is reflected from the shirt. If only blue light is shone onto a red shirt, the shirt would appear black, because the blue would be absorbed and there would be no red light to be reflected. The dyes use absorb light and re-emit it at a different wavelength giving the colors we see on the clothes. The color change happens because the dyes can exist in two states, one of which fluoresces at UV wavelengths and the other at visible wavelengths. The change between the two states is triggered by ultra-violet light. Artificial light contains very little ultraviolet so the dyes revert to the state in which they do not fluoresce in the visible wavelengths. Sunlight contains significant uv and in sunlight the dyes change to the form that fluoresces at visible wavelengths.

That's why the color appears only in sunlight. D. How do haloes, sundogs, primary rainbows, secondary rainbows, and supernumerary bows occur? Haloes Solar halo , which is also called gloriole, icebow or nimbus, is a light phenomenon that happens when light shines through clouds that are composed of ice crystals. Light refracts upon passing through the ice crystals and also reflects upon hitting the crystal’s faces; these events cause the formation of the bright ring around the Sun or Moon. Halo is usually bright white ring but may also have colors due to the dispersion of light upon striking the ice crystals. Below is a picture of a halo produced around the Sun. Sundogs Sundogs, or parhelion (with the sun), happen due to the refraction of light upon hitting the small crystals that make up cirrus or cirrostratus clouds. These crystals are hexagonal in shape and with faces almost horizontal upon drifting; these cause the formation of spots of light (sundog) on either side of the Sun, or the Moon, when light strikes them at a minimum angle of 22 degrees as shown in the image below. Since red light is the least refracted compared to blue this makes the inner edge of a sundog to be red hued. The image below shows an actual sundog which has a red-hued inner edge.

E. Why clouds are usually white and rainclouds dark It's pretty well-known that most clouds are white, while rain clouds are usually a darker shade of gray. But why are rain clouds so dark? Let's start by discussing how clouds form. The air around you is full of water in its gaseous form, called water vapor. When the air near the ground warms, it starts to rise, taking the water vapor along with it. The air starts to cool as it rises higher into the sky, causing the water vapor to condense onto atmospheric dust from volcanoes, car exhaust and other sources. The resulting water droplets and ice crystals coalesce, or join together, to form clouds. Unlike atmospheric particles that scatter more blue light than other colors (making the sky blue), the tiny cloud particles equally scatter all colors of light, which together make up white light. However, rain clouds are gray instead of white because of their thickness, or height. That is, a cloud gets thicker and denser as it gathers more water droplets and ice crystals — the thicker it gets, the more light it scatters, resulting in less light penetrating all the way through it. The particles on the underside of the rain cloud don't have a lot of light to scatter to your eyes, so the base appears gray as you look on from the ground below. This effect becomes more pronounced the larger the water droplets get — such as right before they're large enough to fall from the sky as rain or snow — because they become more efficient at absorbing light, rather than scattering it. It is the thickness, or height of clouds, that makes them look gray. Clouds are made of tiny droplets of water or ice. They are formed when water vapor condenses within pockets of rising air. Under the right conditions, the air continues to be uplifted, causing the cloud to build higher and higher. The tiny water droplets and ice crystals in clouds are just the right size to scatter all colors of light, compared with the smaller molecules of air that scatter blue light most effectively. When light contains all colors, we perceive it as white. When clouds are thin, they let a large portion of the light through and appear white. But like any objects that transmit light, the thicker they are, the less light makes it through. As their thickness increases, the bottoms of clouds look darker but still scatter all colors. We perceive this as gray. If you look carefully, you will notice that the relatively flat bottoms of clouds are always a little grayer than their sides. The taller the clouds become, the grayer their bottoms look. Clouds are visible accumulations of tiny water droplets or ice crystals in the Earth’s

atmosphere. Clouds differ greatly in size, shape, and color. They can appear thin and wispy, or bulky and lumpy. Clouds usually appear white because the tiny water droplets inside them are tightly packed, reflecting most of the sunlight that hits them. White is how our eyes perceive all wavelengths of sunlight mixed together. When it’s about to rain, clouds darken because the water vapor is clumping together into raindrops, leaving larger spaces between drops of water. Less light is reflected. The rain cloud appears black or gray. Clouds form when air becomes saturated, or filled, with water vapor. Warm air can hold more water vapor than cold air, so lowering the temperature of an air mass is like squeezing a sponge. Clouds are the visible result of that squeeze of cooler, moist air. Moist air becomes cloudy with only slight cooling. With further cooling, the water or ice particles that make up the cloud can grow into bigger particles that fall to Earth as precipitation. F. Why is the sky blue? Why are sunsets red? Take a look at light through a prism and notice all the different colors that you can see. Light that looks white to our eyes actually is made up of many different colors. Each color can be thought of as a light wave with a different wavelength (or size). Within the small range of wavelengths (or colors) that we can see with our eyes, the shorter waves are blue and the longer ones are red. Colors such as green, yellow, and orange lie in between the blue and red ends of the visible spectrum. When light comes from the sun, all these light waves of different wavelengths travel through empty space. When they reach Earth’s atmosphere, the light waves can interact with particles in the air like dust, water droplets, and ice crystals. Because of the extremely small size of visible light waves (less than one millionth of a meter), these light waves also interact the tiny gas molecules that make up the air itself. The light waves bounce off these particles just like you might bounce and get jostled in a busy hallway. As the light waves bounce in lots of different directions, we say they have been scattered. How light waves get scattered depends strongly on the size of the particle compared with the wavelength of the light. Particles that are small compared with the light wavelength scatter blue light more strongly than red light. Because of this, the tiny gas molecules that make up our Earth’s atmosphere (mostly oxygen and nitrogen) scatter the blue portion of sunlight in all directions, creating an effect that we see as a blue sky.

more grayish white than blue. Similarly, cloud droplets (typically 10 millionths to 100 millionths of a meter) are much larger than visible light waves, so they scatter light without much color variation. This is why light scattered by clouds takes on the same color as the incoming light. For example, clouds will appear white or gray at midday and orange or red at sunrise or sunset. In this way, clouds act as a screen on which nature’s colors are painted. This is why sunsets or sunrises are so much prettier when some clouds are available to show us the colors. The sun emits light waves with a range of frequencies. Some of these frequencies fall within the visible light spectrum and thus are detectable by the human eye. Since sunlight consists of light with the range of visible light frequencies, it appears white. This white light is incident towards Earth and illuminates both our outdoor world and the atmosphere that surrounds our planet. The interaction of visible light with matter will often result in the absorption of specific frequencies of light. The frequencies of visible light that are not absorbed are either transmitted (by transparent materials) or reflected (by opaque materials). As we sight at various objects in our surroundings, the color that we perceive is dependent upon the color(s) of light that are reflected or transmitted by those objects to our eyes. So if we consider a green leaf on a tree, the atoms of the chlorophyll molecules in the leaf are absorbing most of the frequencies of visible light (except for green) and reflecting the green light to our eyes. The leaf thus appears green. And as we view the black asphalt street, the atoms of the asphalt are absorbing all the frequencies of visible light and no light is reflected to our eyes. The asphalt street thus appears black (the absence of color). In this manner, the interaction of sunlight with matter contributes to the color appearance of our surrounding world. Meanwhile, the light that is not scattered is able to pass through our atmosphere and reach our eyes in a rather non-interrupted path. The lower frequencies of sunlight (ROY) tend to reach our eyes as we sight directly at the sun during midday. While sunlight consists of the entire range of frequencies of visible light, not all frequencies are equally intense. In fact, sunlight tends to be most rich with yellow light frequencies. For these reasons, the sun appears yellow during midday due to the direct passage of dominant amounts of yellow frequencies through our atmosphere and to our eyes. The appearance of the sun changes with the time of day. While it may be yellow during midday, it is often found to gradually turn color as it approaches sunset. This can be explained by light scattering. As the sun approaches the horizon line, sunlight must traverse a greater distance through our atmosphere; this is demonstrated in the diagram below. As the path that sunlight takes through our atmosphere increases in length, ROYGBIV encounters more and more atmospheric particles. This results in the

scattering of greater and greater amounts of yellow light. During sunset hours, the light passing through our atmosphere to our eyes tends to be most concentrated with red and orange frequencies of light. For this reason, the sunsets have a reddish-orange hue. The effect of a red sunset becomes more pronounced if the atmosphere contains more and more particles. The presence of sulfur aerosols (emitted as an industrial pollutant and by volcanic activity) in our atmosphere contributes to some magnificent sunsets (and some very serious environmental problems). III. LEARNING TASKS A. Directions: Encircle the letter that corresponds to the correct answer.

1. What other names are used to mean the light phenomenon halo? Choose

all that apply.

I. Rainbow II. Gloriole III, icebow IV. nimbus

A. I and II C. II, III and IV

B. I, II and III D. All of the above

2. Which of the following correctly describes how a halo looks like?

A. Bright ring formed around the sun or moon.

B. Bright spots of light formed in either side of the sun or moon.

C. An arc of colors that forms opposite the sun.

D. An arc of light composed of green, pink and purple colors

3. In the formation of sundogs, how should the ice crystals (which light

strikes at an angle 22 degrees) be oriented as they drift?

A. The ice crystals are oriented vertically.

B. The ice crystals are oriented horizontally.

C. The ice crystals are oriented diagonally to the right.

D. The ice crystals are oriented diagonally to the left.

4. Why is the inner edge of a sundog red hued?

A. The inner edge of sundog is red hued because red is the color that is

refracted the least.

B. The inner edge of sundog is red hued because red is the color that is

refracted the most.

C. The inner edge of sundog is red hued because red is the color that is

reflected the most.

D. The inner edge of sundog is red hued because red is the color that is

reflected the least.

5. What light phenomenon is seen usually after a rain shower when the

atmosphere is filled with tiny droplets of water?

A. Sundog B. halo C. parhelion D. rainbow

the ice crystals in them?

3. A light phenomenon formed from the combination of several light properties like refraction, reflection, and dispersion?
4. Rainbow are created after a rain shower and.
5. What do you call a visible accumulations of tiny water droplets or ice crystals in the Earth’s atmosphere?
6. How many colors in rainbow?
7. What kind of rainbows are formed when light strikes small raindrops with almost the same size?
8. What kind of rainbows are formed when two inner reflections are done instead of one; this causes the reversal of colors in a secondary rainbow in comparison to a primary rainbow?
9. What do you call as a reflective surface that is curved inward and away from the light source?
10. What kind of mirror are curved outward like the bottom of a spoon? C. Knowledge Checker (1-5 items) Direction: Read and analyze the statement below. Encircle the letter that corresponds your best answer.
    1. The frequency of radio (electromagnetic) waves is measured by _____________. a. Ampere b. Celcious c. Hertz d. Meter
    2. The change in direction of a wave passing from one medium to another. a. Refraction b. Reflection c. Diffraction d. Resonance
    3. Light behaves both like a particle and _______________. a. Current b. Mass c. Field d. Wave
    4. What particles make up light? a. Photons b. Neutrons c. Electrons d. Protons
    5. What property of light allows us to see objects? a. Reflection b. Refraction c. Diffraction d. a, b, c
    6. A green shirt is seen as green because _________________. a. green and red are reflected from the shirt b. yellow and blue are reflected from the shirt c. only green is reflected from the shirt d. all light is reflected from the shirt we just see the green
    7. Which of the following waves is a light wave? a. mechanical b. longitudinal c. infrared d. seismic
    8. What means number of waves per second? a. wavelength b. reflection c. diffraction d. frequency
    9. The bouncing back of a light ray after hitting a surface is known as _________. a. Refraction b. Reflection c. Rebounding d. Diffraction
    10. What causes a yellow fire hydrant appear yellow? a. It absorbs yellow light. b. It transmits yellow light c. It reflects yellow light d. It reflects all colors except yellow

Answer Key:

1. C-Hertz
2. A-Refraction
3. D-Wave
4. A-Photons
5. A-Reflection
6. C-only green is reflected in the shirt
7. C-Infrared
8. D-Frequency
9. B-Reflection
10. C-it reflects yellow

IV. REFLECTION

Instruction: Complete the statement: I have learned that V. REFERENCES aven.amritalearning.com,. (2013). Spherical Mirror. Retrieved 4 June 2020, from aven.amritalearning.com/index.php?sub=100&brch=295&sim=1487&cnt= https://www.physicsclassroom.com/class/refrn/Lesson-4/Mirages https://www1.curriculum.edu.au/sciencepd/readings/ligh_colour.htm https://www.sciencelearn.org.nz/resources/47-colours-of-light https://www.optics4kids.org/what-is-optics/scattering/why-is-the-sky-blue-why-are- sunsets- red#:~:text=Small%20particles%20of%20dust%20and,that%20make%20up%20our %20atmosphere. https://www.sciencelearn.org.nz/resources/47-colours-of-light https://www.physicsclassroom.com/class/light/Lesson-2/Blue-Skies-and-Red- Sunsets https://www.nationalgeographic.org/encyclopedia/cloud/#:~:text=Clouds%20usually %20appear%20white%20because,the%20sunlight%20that%20hits%20them.&text= When%20it's%20about%20to%20rain,Less%20light%20is%20reflected. https://wtamu.edu/~cbaird/sq/2013/01/16/is-light-a-particle-or-a-wave/ https://www.weather.gov/arx/why_halos_sundogs_pillars https://epod.usra.edu/blog/2015/10/primary-secondary-and-supernumerary-rainbows.html#: https://www.quora.com/How-do-hertz-produce-radio-pulses Compiled by: ROWENA LEE P. RADAZA MT II, Science Compiled by: GENGERLYN P. GABRIEL BABAG NATIONAL HIGH SCHOOL - SHS