Grade 5. Practice Test. What is Light? How Light Behaves. Photo Credits (in order of appearance): Alexandr Mitiuc/Dreamstime.com

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1 Name Date Grade 5 What is Light? How Light Behaves Photo Credits (in order of appearance): Alexandr Mitiuc/Dreamstime.com

Today you will read two passages. Read these sources carefully to gather information to answer questions and write an essay. Excerpt from Light by Brian Roberts What is Light?

Scientists usually describe the range of radiant energy as a spectrum, or a series of energy bands.

Violet 2 The diagram above shows all the major bands of radiant energy. Visible light bands are in the middle of this spectrum. But they are only a small part of it.

2 Today you will read two passages. Read these sources carefully to gather information to answer questions and write an essay. Excerpt from Light by Brian Roberts What is Light? 1 Light is a form of energy called radiant energy. But the light you can see is only one kind of radiant energy. Scientists usually describe the range of radiant energy as a spectrum, or a series of energy bands. KINDS OF RADIANT ENERGY Low Frequency High Frequency Long Wavelength Radio TV Microwaves Infra Red Waves Ultra Violet Short Wavelength X-ray Gamma Detail of Visible Light Red Orange Yellow Green Blue Violet 2 The diagram above shows all the major bands of radiant energy. Visible light bands are in the middle of this spectrum. But they are only a small part of it. On each side of visible light are bands representing invisible radiant energy. Those on the left have less energy than the bands on the right side. This means that gamma rays are much more powerful than radio waves. Sunlight is actually a mixture of many colors. Light passing through a prism is separated into many bands of color. These are the same colors seen in a rainbow. 3 Scientists have two ways to describe light and how it moves. The first way describes light as tiny, invisible particles, or packets, of energy called photons. Because photons are energy, and not matter, they have no weight. Even a billion photons have no weight. 1 of 10

3 4 Not all photons are equal. High-powered radiant energy, such as gamma rays, have photons that carry more energy than photons of visible light. Even in visible light, one color of light might have more energy than another. For example, violet light photons carry more energy than red light photons. COMPARING COLORS OF LIGHT Red Light Violet Light Violet light photons have shorter wavelengths than red light photons, and more energy. 5 Light is also described as moving in waves. These waves are measured in terms of their frequency, or how closely together they travel. High-frequency waves travel more closely together. This means that more of them pass a given point in a period of time than low-frequency waves, which are more spread out. Scientists measure frequency by a property called wavelength. Wavelength is the distance between the peak of one wave and the peak of the wave next to it. 6 Look at the diagrams of a high-frequency wave and a low-frequency wave. The low-frequency waves are more spread out. They have a longer wavelength. The longer the wavelength is, the lower the wave s energy. WAVELENGTHS High Frequency Wave Low Frequency Wave 2 of 10

4 7 There are several things that you should know about the movement of light. One is that it travels in a straight line. A second is that beams or rays of light can change direction. 8 There is a third important thing you should know about light s movement. Unlike sound, light does not need a medium such as air, water, or wood to travel through. This is what makes radiant energy so special. It can travel through the nothingness of space. If it were not for this special property of radiant energy, sunlight would never reach Earth. 9 Perhaps the most impressive thing about how light travels is its speed. Nothing is faster. In fact, light moves so fast through space that it goes 300,000 km (186,000 mi) in a single second. This is much faster than sound. bk Since light travels so fast and over such great distances in space, scientists have come up with a special unit called a light-year. It is the distance light travels in one year. So how far is that, you ask? About 9.5 trillion kilometers (5.9 trillion miles)! 1. Part A On the basis of the text and diagram, how many major bands of radiant energy are there? A 6 B 7 C 8 D 9 or more How many of these major bands of radiant energy are invisible? A 6 B 7 C 8 D 9 or more 2. Part A Which word is used to describe a series of energy bands? A frequency B photon C spectrum D wavelength Which word is used to describe a particle of light? A frequency B photon C spectrum D wavelength 3 of 10

5 3. Part A Which word is used to describe how closely together waves of light travel? A frequency B photon C spectrum D wavelength Which word is used to describe the distance between peaks in waves of light? A frequency B photon C spectrum D wavelength 4. Which of the following statements about light and sound are true? Choose all that apply. A Sound moves faster than light. B Sound moves slower than light. C Light can move through the nothingness of space. D Sound can move through the nothingness of space. E Light can move like a particle. F Light can move in waves. 5. According to the text, what does a light-year measure? A distance B time C frequency D wavelength 4 of 10

6 Excerpt from Light by Brian Roberts How Light Behaves 1 Light behaves in different ways when it strikes different materials and surfaces. Sometimes light simply passes through clear materials. These materials are called transparent. Some materials do not let any light pass through. These materials are called opaque. Opaque materials absorb or reflect the light that strikes them. Then there are cases when only some of the light passes through a substance. These materials are called translucent. Transparent objects let all light through. Opaque objects block all light. Translucent objects do both. They block some light waves and let others through. 2 We see most things because of the light that bounces off them. Scientists have observed light reflecting from a smooth surface. Light bounces off a surface at the same angle at which it strikes the surface. If the surface is very smooth, like a mirror, light reflects in a regular pattern. Everything looks normal. This explains why standing in front of a smooth, flat mirror allows you to see a perfect image of yourself. 3 If a surface is uneven, on the other hand, light scatters in many different directions. That s why sunlight sparkles off ocean waves. The waves create many angles on the water s surface. These angles reflect and scatter light in many directions. 4 Because opaque objects reflect or absorb light, they cast shadows. A shadow occurs behind an opaque object because light cannot get through the object to the area behind it. The farther an object is from the surface the shadow falls upon, the larger the shadow the object casts. The size of the shadow also depends on the angle and distance of the light. If a light source is far from or directly above an object, the object will cast a small shadow. But if the light is close to or beside the object, its shadow will be bigger. That s why you cast a bigger shadow when the sun is lower in the sky. 5 of 10

$5 When light passes from one transparent material to another, like air to water, it changes speed and bends. This bending of light rays is called refraction.$

7 5 When light passes from one transparent material to another, like air to water, it changes speed and bends. This bending of light rays is called refraction. Some materials cause more refraction than others. For example, water slows the speed of light more than air does. The different speeds of light through water and air can make something sticking out of water look bent even though the object is really straight. Convex Lens Lenses Concave Lens Light also refracts when it passes through transparent lenses of different shapes. The diagrams show what happens when light passes through a concave lens or a convex lens. Convex lenses focus light, and concave lenses spread light out. Convex lenses focus light, and concave lenses spread light out. 6 of 10

7. Which is an example of reflection? A light sparkling off a shiny object B light going through a convex lens C light going through a concave lens D light passing through air into water 6.

8 7. Which is an example of reflection? A light sparkling off a shiny object B light going through a convex lens C light going through a concave lens D light passing through air into water 6. Part A Which word best describes the picture of the window shown above? A opaque B transparent C colorful D translucent Which word best describes the picture of the book shown above? A opaque B transparent C colorful D translucent Part C Which word best describes the picture of the vase shown above? A opaque B transparent C colorful D translucent 8. Part A What is the main idea of paragraph 5? A Light rays can bend. B Light can travel at different speeds. C Both air and water are transparent. D Light passes through transparent materials. Which sentence from the paragraph best supports the correct answer to Part A? A When light passes from one transparent material to another, like air to water, it changes speed and bends. B Some materials cause more refraction than others. C For example, water slows the speed of light more than air does. D The different speeds of light through water and air can make something sticking out of water look bent even though the object is really straight. 7 of 10

9 9. Write a paragraph that explains one way reflection and refraction are alike and one way they are different. 10. Part A On the basis of the lenses diagram, what causes one lens to spread light out and another to focus light? A the speed of the light B the distance from the light C the shape of the lenses D the size of the lenses Which paragraph in What is Light best describes what happens in this diagram? A paragraph 1 B paragraph 4 C paragraph 7 D paragraph 8 8 of 10

10 11. You have read two texts about light energy. Summarize the main ideas in each text and explain how the texts work together to give a more complete understanding of light energy. Be sure to include examples from both texts to support your ideas. 9 of 10

11 : Answer Sheet 1. Part A 2. Part A 3. Part A 4. E F Part A Part A 9. Constructed Response 10. Part A 11. Constructed Response 10 of 10

Answer Key Grade 5. Practice Test. What is Light? How Light Behaves

Answer Key Grade 5. Practice Test. What is Light? How Light Behaves Answer Key Grade 5 What is Light? How Light Behaves 1. Part A Based on the text and diagram, how many major bands of radiant energy are there? A Incorrect. Look at the Kinds of Radiant Energy diagram.