Practice Questions: Light, Shadow and Reflections | Practice Questions with Solutions for Class 6 PDF Download

Q1: Which of the following devices is used to image the sun?
(a) Plane mirror
(b) Pinhole camera
(c) A straight pipe
(d) Electric bulb
Ans: (b)
Sun can be imaged using a pinhole camera.

Q2: Explain the construction of a pinhole camera.
Ans: The pinhole camera is made up of two boxes that fit together perfectly without any gaps. One side of each box has been ripped out. A small pinhole is made in the centre of the larger box’s opposite side, and a small square is glued to the smaller box’s opposite surface. Translucent paper is wrapped around a sliced portion. As the smaller box slides into the larger box, the pinhole in the smaller box faces the square strip. The open face of the small box is used to observe objects while blocking out light from behind. The smaller box can be dragged back and forth until the image is in focus.

Q3: What are the primary characteristics of a pinhole camera?
Ans: The  five characteristics of a pinhole camera  are:

• The colour of the image remains the same as the colour of the object.
• The image formed on the screen of the pinhole camera is real.
• The size of the object can be greater, same or less  than the size of the real object.
• The image resulted in a pinhole camera  inverted.
• Pinhole cameras can also be used to click photos and display them on screens.

Q4: Define obstacles.
Ans: Any object which blocks the path of light is called an obstacle. It’s the presence of obstacles in the path of light that results in shadow formation.

Q5: What materials are needed for the shadow formation?
Ans: Materials needed for shadow formation are:

• Source of light
• Screen
• An opaque object obstructing the path of light
  
  

Q6: You are given a transparent glass sheet. Suggest two ways to make it translucent without breaking it.
Ans: We can convert transparent glass sheets into translucent glass sheets without breaking it in following ways:

• By applying  oil, grease, butter or vaseline to make it partially permeable.
• By making the surface of the glass rough by scrubbing it with sandpaper which allows the light to pass partially.

Q7: Define the following terms:

1. Luminous objects
2. Non-Luminous objects
3. Transparent
4. Translucent
5. Opaque

Ans:

1. Luminous objects: Objects which can produce their own light are known as luminous objects—for example, the sun, star, moon, and candle. 
2. Non-Luminous objects: Objects which can not produce their own light are known as non-luminous objects, for example, doors, cloth, wood etc.
3. Transparent: Objects which allow light to pass through them completely are called transparent objects. We can clearly see  through them. For example, glass, clear water, lens.
4. Translucent: Objects which allow light to pass through them partially are called translucent objects. We can see objects partially through translucent objects. For example oiled paper, coloured glass panes etc.
5. Opaque: Objects which do not allow any light to pass through them at all are called opaque objects. For example metal, wood etc.

Q8: Is the air around us always transparent? Discuss.
Ans: The air around us is usually transparent. This is the reason we can see the buildings and trees around us. When the air gets polluted, and smoke and dust particles get mixed with the air, the transparency of air decreases as the pollutant particles absorb light.

Q9: What is a mirror? Explain its functioning.
Ans: Mirror is a smooth, shiny surface which reflects light rays to form a clear image of an item. It is made up of glass with a mirror coating on one side. The image formed in the mirror is created by the reflecting of light rays off the surface of the mirror. The light rays coming from the object hits the mirror and bounces off at an angle. The image of the object in the mirror is created by the reflection of light rays. Reflections cause the images generated to be laterally inverted.

Q10: Using a pinhole camera, a student observes the image of two of his friends, standing in the sunlight, wearing yellow and red shirts, respectively. Comment on the colours of the shirts in the image?
Ans: Pinhole camera doesn’t change the colour of the image. The colour of the shirt in the image will remain the same as the colour of the object. Although the image of the person will be inverted when seen through the pinhole camera.

Q11: Classify the following objects/materials given below as
(i) opaque, transparent or translucent
(ii) non-luminous or luminous
Air, water, a piece of rock, a sheet of aluminium, a mirror, a wooden board, a sheet of polythene, 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, the moon.
Ans:

• Opaque objects: A piece of rock, a sheet of carbon paper, or a sheet of cardboard, a sheet of aluminium, a mirror, a wooden board, a CD, an umbrella, a wall
• Transparent objects: A sheet of plane glass, air, water.
• Translucent objects: A sheet of polythene, smoke, fog, a sheet of cellophane, and a wire mesh.
• Luminous objects: A piece of red hot iron, a lighted torch, sun, firefly, kerosene stove, a lighted fluorescent tube, the flame of a gas burner.
• Non–luminous objects: Air, water, a piece of rock, a sheet of aluminium, a mirror, a wooden board, a sheet of polythene, a CD, smoke, a sheet of plane glass, fog, an umbrella, a wall, a sheet of carbon paper, a sheet of cardboard, a sheet of cellophane, a wire mesh, moon.

Q12: Which of the following objects given below is not always necessary to observe a shadow?
(a) Sun
(b) Screen
(c) Source of light
(d) Opaque object
Ans: (a)
Sun is not always necessary for observing a shadow. A source of light is essential for shadow formation, and the sun is a source of light.

Q13: If you hold up a mirror in front of you in a completely dark room, will you see a reflection of yourself in the mirror?
Ans: In a completely dark room, if we hold up a mirror in front of us, we can’t see a reflection of ourselves in the mirror as the light will not fall on the mirror to reflect light due to darkness.

Q14: Mansi observed the shadow of a tree at 8:00 a.m., 12:00 noon and 3:00 p.m. Which of the following statements is near to her observation about the shape and size of the shadow of the tree she observed?
(a) The size of the shadow remains the same but the shape of the shadow of the tree changes.
(b) Neither the shape nor the size of the shadow changes.
(c) The size and shape of the shadow of the tree changes at different intervals of time.
(d) The size of the shadow of the tree changes, but the shape remains the same.
Ans: (c)
As the earth revolves and rotates around the sun, the position of the sun changes. Sun being the light source, as the position of the light source changes, accordingly, the size and the shadow of the tree also changes.

Q15: Correct the following statements given below:
(i) The colour of the object determines the colour of the shadow.
(ii) Transparent objects allow light to pass through them partially.
Ans: (i) The colour of the shadow of a given object does not depend on the colour of the object, as the shadows are always dark.
(ii) Translucent objects are objects which allow light to pass through them partially, and transparent objects allow light to pass through them completely.