Light, Shadows and Reflections
KEYWORDS
• Luminous object: an object that gives out the light of its own is called luminous object.
• On the Luminous object: the object that does not emit its own light but only reflects the light of other sources.
• Light: a form of invisible energy that gives us the sensation of sight.
• Reflection: a phenomenon in which light bounces off an object.
• Transparent: a medium which allows light to pass through it.
• Mirror: a thin, flat and smooth sheet of glass having a shiny coating on one side.
• Shadow: an area of darkness formed by an opaque object obstructing light.
• Umbra: the darkest part of the shadow where no light reaches.
• Solar eclipse: the shadow of the moon falling over the whole or any a part of the teeth.
• Rectilinear propagation of light: the property of light travelling in a straight line.
•Opaque: a medium which does not allow light to pass through it.
•Translucent: a medium which allows light to pass through it partially.
• The source of light: an object which gives out the light.
POINTS TO REMEMBER
• Light is a form of energy.
• Luminous objects emit light. We see them by the light they emit. Non-luminous objects do not emit light. We see them by the light they reflect.
• Light travels in straight line. It spreads out in all directions from a source of light.
• The source of light can be natural or man-made.
• The objects that emit light are called
luminous objects and that do not emit light are called non-luminous objects.
• The opaque objects from the shadow as they do not allow the light to pass through them.
• A ray represents the path taken by light. A beam consists of a large number of rays.
• The bouncing off light is called reflection.
• The dark part of a shadow that receives no light from the source is called umbra. The partial shadow surrounding the umbra is called the penumbra.
• Object are transparent when they allow light to pass through them.
• The image formed by pinhole camera is real and inverted.
• The pinhole camera is a simple device that can use to measure the height of an object.
• The solar eclipse occurs when the moon happens to come in between the sun and the earth. A solar eclipse can be total or partial.
• The formation of an image in a pinhole camera gives evidence of the theory of rectilinear propagation of light.
Multiple Choice Questions
1. Which of these is not a source of light?
(a) Sun
(b) Fire
(c) Star
(d) Moon
2. Which of the following is not a translucent object?
(a) Cellophane paper
(b) Ground glass
(c) Butter paper
(d) Tissue paper
3. Which of the following is not an artificial source of light?
(a) Candle
(b) Electric
(c) Sun
(d) None of these
4. Which of the following are non-luminous bodies?
(a) Moon
(b) Incandescent lamps
(c) Rock
(d) None of these
5. Materials which allow light to pass through them are called
(a) translucent
(b) transparent
(c) opaque
(d) all of these
6. The object which does not allow light to pass through it is called
(a) opaque
(b) transparent
(c) translucent
(d) none of these
7. Which of the following material allows light to pass through it?
(a) Copper
(b) Wood
(c) glass
(d) Walls
8. Sunlight can pass through
(a) bushy tree
(b) rocks
(c) water
(d) walls
Ans:
1. (d) 2. (b) 3. (c) 4. (c) 5. (b) 6. (a) 7. (c) 8. (c)
Fill in the blanks :
1. The main source of light on earth is the———–.
2. All source of light is———– objects.
3. Substances that allow most of the light to pass through them are called—————- substances.
4. If we place an object in the path of light, a —————-is formed.
5. A very—————– beam of light is known as a ray of light.
Ans:
1. The main source of light on earth is the sun.
2. All source of light is luminous objects.
3. Substances that allow most of the light to pass through them are called transparent substances.
4. If we place an object in the path of light, a shadow is formed.
5. A very narrow beam of light is known as a ray of light.
State whether ‘True’ or ‘False’
1. The image formed by a plane mirror is always of the same size as the object.
2. Non-luminous bodies reflect all the light that falls on them.
3. A solar eclipse occurs when the moon’s shadow falls on the earth.
4. Opaque objects allow all the light that falls on them to pass through them.
5. Light takes several years to travel from the earth.
Ans:
1. True, 2. True, 3. True, 4. False, 5. False
Very Short Answer Questions?
1. What are luminous objects? Give two examples.
2. Name any two man-made luminous bodies.
3. Name three opaque materials.
4. Name two transparent objects.
5. What is light?
6. What is a shadow?
7. Define reflection.
Ans:
1. The object that gives out its own light is called a luminous object Are—sun, stars
2. Bulb, tube light
3. Rock, wood, wall
4. Glass, water
5. Light is a form of energy which helps us to see.
6. A shadow is a dark space (shade) formed behind an opaque object when it blocks light from any source.
7. The bouncing back of light rays from the surface of an object is called reflection.
CLASS VI SCIENCE