Light Shadows and Reflections BOSEM Class 6 Science

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Light Shadows and Reflections – BOSEM Class 6 Science: Explore key concepts of light, shadow formation, and reflection with examples. Perfect for exam prep and understanding basics in the BOSEM curriculum.

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Light Shadows and Reflections Notes

  • Light is an energy that helps us see objects.
  • Objects can be grouped as luminous or non-luminous depending on whether they have their own light or not.
  • Luminous object are those object that gives out or emit light of their own.
    Example: Sun, torch etc.
  • Non-luminous objects are those objects that do not emit light of their own.
    Example: Chair, table etc.
  • Objects can also be grouped as opaque, transparent and translucent depending on the light
    towards them.
  • Opaque objects are those objects that do not allow light to pass through them.
    Example: Table, chair, tree etc.
  • Transparent object are those object that allows light to pass through them.
    Examples: Glass, polythene etc.
  • Translucent objects are those objects that allow some of the light to pass through them.
    Examples: Butter paper, tissue paper etc.
  • Shadow is the black patch formed when an opaque body blocks the source of light.
  • We need a source of light, an opaque object, and a screen to see shadows.
  • No shadows are formed in the absence of light.

The characteristics of a shadows are

  • The shadow is always erect.
  • The shadow is always black irrespective of the colours of the object.
  • The shape of the shadow changes depending on the angle at which the light falls on the object.
  • The size of the shadow depends on the distance of the source of light.
  • The shadow can be seen only on a screen.

Pinhole Camera: A pinhole camera is just a box with a very tiny hole on one of its sides. Light falls on the hole and an inverted image is formed on the opposite side of the hole.

The properties of the image formed by the pinhole camera are:

  1. The image is of the same colour as the object.
  2. An upside-down (inverted) image is formed.
  3. The image so formed is smaller in size.

The condition required to get a clear image through the pinhole camera are:

  1. The objects should be placed in the bright sunlight.
  2. A black cloth should cover the head and the pinhole camera.
  3. The pinhole should be small.
  • The movement of the sun can be observed by using a pin-hole camera. Even the phenomenon of a solar eclipse can be seen using this device.
  • With a pinhole camera, we can view images of various objects like trees, buildings etc.
  • During a solar eclipse, we should never look directly at the sun as looking at it directly could buildings
    be harmful to our eyes.
  • Sometimes, we come across with natural pinhole camera on bright sunny days when we pass under a tree covered with several leaves. The circular patch of sunlight seen under the tree is the pinhole image of the sun where the gaps between the leaves act as pinholes.
  • Light travels in a straight line.
  • A mirror is a smooth surface that can make an image.
  • The phenomenon of bouncing back of light from a smooth surface is known as reflection.
  • Mirror changes the direction of light that falls on it.

Light Shadows and Reflections Questions and Answers

Q1. Rearrange the boxes given below to make a sentence that helps us understand opaque objects.

OWSAKE
OPAQUEO
BJECTSM

Ans: OPAQ|UEO|BJEC|TSM|AKSHAD|OWS

Q2. Classify the objects or materials given as opaque. transparent or translucent and luminous or non-luminous.
Air, water, a piece of rock, a sheet of aluminium, a mirror, a wooden board, a sheet of polyethene, a CD, smoke, a sheet of plane glass, fog. a piece of red hot iron, an umbrella, a lighted fluorescent tube, a wall, a sheet of carbon paper, the flame of a gas burner, a sheet of cardboard, a lighted torch, a sheet Of cellophane, a wire mesh, kerosene Stove, sun, firefly, moon.

ObjectsOpaque/Transparent/TransclucentLuninous/Non-Luminous
AirTransparentNon-Luminous
WaterTransparentNon-Luminous
A piece of rockOpaqueNon-Luminous
A sheet of aluminiumOpaqueNon-Luminous
A mirrorOpaqueNon-Luminous
A Wooden BoardOpaqueNon-Luminous
A Sheet of polytheneTransparent/ Translucent
(Depends on coloured or colourless)		Non-Luminous
A CDOpaqueNon-Luminous
SmokeTranslucentNon-Luminous
A sheet of Plane GlassTransparentNon-Luminous
FogTranslucentNon-Luminous
A piece of red-hot ironOpaqueLuminous
An UmbrellaOpaqueNon-Luminous
A light fluorescent tubeOpaqueLuminous
A wallOpaqueNon-Luminous
A sheet of carbon paperOpaqueNon-Luminous
The Flame of a Gas BurnerOpaqueLuminous
A sheet of cardboardOpaqueNon-Luminous
A lighted torchOpaqueLuminous
A wire meshOpaqueNon-Luminous
KeroseneTranslucentNon-Luminous
SunOpaqueLuminous
FireflyOpaqueLuminous
MoonOpaqueNon-Luminous

Q3. Can you think of a shape that would give a circular shadow if held in one way and a rectangle shadow if held in another way?

Ans: Yes, the shape can be a cylinder. A circular or rectangular shadow is formed depending on the angle at which the light falls on the cylinder.

Q4. In a completely dark room, if you hold up a mirror in front of you, will you see a reflection of yourself in the mirror?
Ans: No, I will not see a reflection of myself in the darkroom because there is no light. As such, no reflection will take place, and no image will be formed.

Extra questions and answers: Light Shadows and Reflections

1. Name some natural sources of light.
Ans: Sun, stars, fireflies etc.

2. Name some man-made sources of light.
Ans: Electric bulb, tube light, candle, torch etc.

3. Differentiate luminous and non-luminous objects.
Ans

Luminous objectNon-luminous object
An object which gives out its own light is called a luminous object.An object which does not give out its own light is called a non-luminous object.
Example: Sun, star, electric bulb etc.Example: Table, chairs, pen, pencil etc.



4. Define the following terms:
(a) Transparent object
(b) Opaque object
(c) Translucent object

Ans:
(a) Those materials which allow light to pass through them is called transparent object.
Example: glass.

(b) Those materials which do not allow light to pass through them is called opaque object.
Example: stone.

(c) Those materials which allow some of the light to pass through them are called translucent object.
Example: butter paper.

5. Define shadow. What are the conditions required to see a shadow?
Ans: Shadow is the black patch formed when an opaque body blocks the source of light.
The conditions required to see a shadow are (i) a source of light (ii) an opaque object and (iii) a screen.

6. Why cannot we see an object placed in a dark room?
Ans: Because there is no light.

7. Write the characteristics of a shadow.
Ans: The characteristics of a shadow are
(i) The shadow is erect.
(ii) The shadow is always black irrespective of the colour of the objects.

Extra Questions and Answers 2

1. Why can we see objects around us?
Ans: We can see objects around us because light reflects off these objects and enters our eyes, allowing us to perceive them.

2. How does the size of a shadow change throughout the day?
Ans: The size of a shadow changes throughout the day depending on the position of the sun. In the morning and evening, shadows are long, while at noon, when the sun is overhead, shadows are shortest.

3. What is rectilinear propagation of light?
Ans: Rectilinear propagation of light is the principle that light travels in a straight line.

4. How can you tell if an object is transparent, translucent, or opaque?
Ans:

  • If light passes completely through an object, it is transparent.
  • If light passes partially through an object, it is translucent.
  • If no light passes through an object, it is opaque.

5. Why do shadows form on the opposite side of a light source?
Ans: Shadows form on the opposite side of a light source because the object blocks the path of light, preventing it from reaching that area, which creates a dark patch.

6. Give examples of objects that form sharp and blurry shadows.
Ans:

  • Sharp shadows: Shadows formed by small and strong light sources, like a torch or the sun on a sunny day.
  • Blurry shadows: Shadows formed by large or diffused light sources, like an overcast sky or a soft lamp.

7. What is the difference between a shadow and an image?
Ans:

  • Shadow: Formed when an object blocks light; it is always black regardless of the object’s color.
  • Image: Formed by the reflection or refraction of light; it shows the actual colors and details of the object.

8. Explain why shadows are longer in the morning and evening.
Ans: Shadows are longer in the morning and evening because the sun is at a lower angle in the sky, and light strikes objects at a slant, creating elongated shadows.

9. What is a source of light? Give examples of natural and artificial sources.
Ans: A source of light is an object that emits light.

  • Natural sources: Sun, stars, fireflies.
  • Artificial sources: Bulbs, lamps, candles.

10. What is the role of a screen in observing shadows?
Ans: A screen is necessary to observe shadows because it captures the shadow formed by the object blocking light. Without a screen, the shadow would not be visible.

11. Why can’t transparent objects form shadows?
Ans: Transparent objects cannot form shadows because they allow light to pass through them completely, leaving no dark patch.

12. What kind of shadow is formed if the light source is far from the object?
Ans: If the light source is far from the object, a smaller and sharper shadow is formed.

13. Why is the shadow always black, even if the object is coloured?
Ans: A shadow is always black because it is simply the absence of light. Shadows do not capture the color of the object, only the outline.

14. Describe a practical way to make a simple pinhole camera.
Ans:

  • Take a small box and cover it with black paper to make it dark inside.
  • Make a small hole in one side of the box.
  • Place a white paper on the opposite side as the screen.
  • When light passes through the pinhole, it forms an inverted image of any object outside on the screen.

15. Why do we use mirrors in our daily lives?
Ans: We use mirrors to see our reflection, which helps us in personal grooming, dressing, and checking our appearance.

16. What are the main differences between a plane mirror and a pinhole camera?
Ans:

  • A plane mirror forms a virtual, upright image, while a pinhole camera forms a real, inverted image.
  • Mirrors require light to reflect from an object to form an image, whereas a pinhole camera uses a small hole to direct light to form an image.

17. How does a shadow’s shape change if the angle of the light source changes?
Ans: If the angle of the light source changes, the shape of the shadow also changes because the shadow elongates or shortens based on the angle at which light falls on the object.

18. Explain how a solar eclipse forms using the concept of shadows.
Ans: A solar eclipse forms when the moon passes between the Earth and the sun, blocking sunlight from reaching parts of the Earth and casting a shadow on the Earth’s surface.

19. Why does light not pass through opaque objects?
Ans: Light does not pass through opaque objects because their material composition absorbs or reflects light, preventing it from passing through.

20. How can we make an object visible in a dark room?
Ans: We can make an object visible in a dark room by shining a light on it, as light reflects off the object and reaches our eyes, making it visible.

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