Very Short-Answer Questions:
Q. 1: Name one man-made luminous body.
Ans. Electric bulb.
Q. 2: Is grounded glass is transparent? If not, what type of substance it is ?
Ans. Grounded glass is not transparent. It is a translucent type of substance.
Note: Glass is the smooth surface whereas, the ground (past tense of the grind) glass is very rough and flat surface and so it does not have the smooth surface and has lots of scratches on it which scatters the light falling on it without allowing the light to enter and pass through it.
Q. 3: Are stars are luminous or nonluminous ?
Ans. Stars are luminous.
Q. 4: Can transparent object cast shadow ?
Ans. No.
Q. 5: What will be the colour of a shadow of a coloured object ?
Ans. The shadow of a colored object is always black.
Q. 6: Which of the two image or shadow, formed by the light reflected from the object ?
Ans. Image.
Short – Answer Questions:
Q. 1: What is light ? Is the speed of light greater than speed of sound ?
Ans.1: Light is a form of energy which causes the sensation of vision in our eyes. The speed of light is faster than sound. Because light doesn't need a medium to travel.
Q 2: Why nonluminous bodies become visible when light from some other source is made to fall on them ?
Ans. 2: Nonluminous bodies become visible due to the reflection or scattering of light falling on them from any luminous body.
Q. 3: What equipment or materials are needed to show the formation of shadow?
Ans. 3: The formation of shadow requires the following material:
1) A source of light
2) An opaque object
3) Any surface or a screen behind the object
Q. 4: Write tow characteristics of a shadow.
Ans. 4: Two characteristics of shadow are as follows:
1) They are always dark in colour.
2) They are formed opposite to the source of light.
Q 5: Write one advantage and one disadvantage of a pinhole camera.
Ans. 5: Advantage: no focusing is required.
Disadvantage: the image formed does not give any details.
Long Answer Type Questions:
Q. 1: Write the conditions required for a shadow to form.
Ans. 1: The required conditions to form a shadow are:
- The object should be opaque where light cannot pass through.
- Source of light and a screen is needed for the formation of shadow.
- The opaque object should be placed in between the source of light and screen.
Q. 2: What is meant by reflection of light?
Ans.2: The process through which light rays falling on the surface on an object are sent back is called reflection of light. Thus, when light falls on the surface of an object it sends back the light. The objects having shiny or polished surface reflects more light compared to the objects having dull or unpolished surface.
Q. 3: Can you think of crating a shape that would give a circular if held in one way and a rectangle shadow if held in another way ?
Ans.3: Yes, there are many objects like a cylinder and a circular disc, which would give a circular shadow if held in one way and a rectangular shadow if held in another way.
(a) Circular shadow with cylinder
(b) Rectangular shadow with cylinder
Q. 4: Show the reflection of light by a plane mirror.
Ans. 4:
Ans. 4:
S. No. | Image | Shadow |
1 | Image is formed due to the reflection or refraction of light | Shadows are formed when opaque objects obstruct the path of light. |
2 | Image is seen when light comes from the object after reflection or refraction enters the observer's eye. | No light enters the eye from the shadow of the object. |
3 | Image gives more information such as colour, structure, etc. about the object. | Shadow does not provide any details about the object but it gives an idea about the shape of the object. |
Define the following terms:
1. Luminous body and Nonluminous body
2. Mirror
3. Reflection of light
4. Transparent material
5. Translucent material
Ans.
1. Luminous body: The bodies which have its own source of energy to emit light are called luminous bodies. Example: Stars, burning candle, sun, etc.
Nonluminous body: The bodies which are not able to emit light but are visible only when they reflect light produced by the luminous objects are called non-luminous bodies. Example: earth, blackboard, moon.
2. Mirror: A mirror is a smooth surface on which regular reflection takes place. A clear image of an object placed in front of a mirror is formed due to reflection of light. Generally a mirror is prepared by giving metal coating on one surface of glass. This process of coating with mercury or silver on glass is called silvering.
3. Reflection of light: The process through which light rays falling on the surface on an object are sent back is called reflection of light. Thus, when light falls on the surface of an object it sends back the light. The objects having shiny or polished surface reflects more light compared to the objects having dull or unpolished surface.
4. Transparent material: A material through which light can pass completely is called transparent material. We can clearly see through these objects. They can also be called see-through objects. An object on the other side of this material is clearly visible. Example: glass, water, air etc.
5. Translucent material: A material through which light can pass partially is called translucent material. We can partly see through these objects. They can also be called partially-see-through objects. An object on the other side of this material is visible to some extent.
Extra Questions:
Q.1: How does the colour of an opaque object affect the colour of the shadow?
Ans: Shadow is the dark area behind any opaque object where the light cannot pass through. The colour of an opaque object doesn’t affect the colour of the shadow.
Q.2: What do you mean by scattering of light?
Ans: When light rays enter a rough medium like gases, the light rays get deflected in random directions. This is known as scattering of light.
Q.3: If you have ever seen an ambulance, the word ‘AMBULANCE’ is written in the form of mirror image in vehicles. Why is it so?
Ans: Word AMBULANCE is written reverse as because the mirror shows a property of what we call in scientific terms is "lateral inversion".
It is a phenomenon in which when an object is placed in front of the mirror the right side of the object becomes left side of the image and the left side of the object becomes right side of the image, therefore the already written inverse AMBULANCE when viewed through the rear view mirror of the vehicle then the driver could easily get to know about the ambulance and give way to it.