Light
1) What is light?
Ans:
Light is a form of energy that gives the sensation of sight/vision.
2) What is
the speed of light in vacuum or air?
Ans:
The speed of light in vacuum or air is 3x108m/s.
3) What is
ray?
Ans:
The narrow path of light which is represented by a straight line with an arrow
is called a ray of light.
4) What is
reflection of light? Show with diagram.
Ans:
The process of returning light to the same medium after striking on a surface
is called reflection of light.
5) State
the laws of reflection of light.
Ans:
When light falls on a surface, it follows the following laws;
§
Incident
ray, reflected ray and normal lie on the same plane.
§
Angle
of incident is equal to the angle of reflection.
6) Define regular and irregular reflection.
Ans:
Regular Reflection:When a parallel beam of light strikes on a surface and reflected to light is also parallel then it is said to be regular reflection. Irregular Reflection:The phenomenon of returning a parallel beam of incident light in different directions after striking on a surface is called irregular reflection.
4) What is mirror? Mention its types.
Ans:
Mirror is a smooth surface which forms an image due to reflection of light. It is of two types:
- Plane Mirror
- Curved Mirror
5) What do you mean by plane mirror?
Ans:
The mirror whose surface is smooth plane in which reflection occurs is called plane mirror.
6) Write any four characteristics of image formed by plane mirror.
Ans:
The following are the characteristics formed by plane mirror;
- Image is same size as that of object.
- Image distance and object distance is equal.
- Image is laterally inverted.
- Image is virtual and erect.
7) What do you mean by convex and concave mirror?
Ans:
Convex Mirror: A spherical mirror whose outer surface is reflecting surface is called convex mirror.
Concave Mirror: A spherical mirror whose inner surface is reflecting surface is called convex mirror.
8) What are real and virtual image?
Ans:
Real image is an image which is obtained on a screen. Virtual image is an image which can not be obtained on the scree.
9)Distinguish
between real and virtual image.
Ans:
|
S.No
|
Real Image
|
Virtual Image
|
|
1
|
This can be obtained on the screen.
|
This cannot be obtained on the screen.
|
|
2
|
This has real existance.
|
This does not have real existance.
|
10.)Convex mirror is used as rear-view or side mirror in a vechile, why? (2073 Jhapa)
Ans:
Convex mirror is used as rear-view in a vechile because it forms smaller image than the objects so that large number of objects can be seen at a time even in small mirror.
11)Distinguish
between Concave and convex mirror.
Ans:
|
S.No
|
Concave Mirror
|
Convex Mirror
|
|
1
|
Its outer surface is polished.
|
Its inner surface is polished.
|
|
2
|
It may give magnified or diminished image.
|
It gives diminished image only.
|
|
3
|
It forms real image except when object is in between focus and pole.
|
It forms virtual image.
|
12)What is the cause of refraction of light?
Ans:
Velocity of light is different in different media so that while passing from one medium to another velocity changes and refraction occurs.
13)State the law of refraction of light.
Ans:
The following are the laws of refraction of light:
- Lights bends towards normal when passes from rarer medium to denser medium and bends away from normal when passes from denser to rarer medium.
- The incident ray, the normal ray and the reflected ray all lie on the same plane.
DLE Questions Solved
1)Complete the given ray diagram and write any two nature of the image formed. (2073 Banke)(2072 Jhapa)
Nature of Image formed:
- Image is real.
- Image is inverted.
2)What is refraction of light? Draw a ray diagram to show the image formed when the object is placed at C in front of a concave mirror. Also mention its two nature of image. (2073 Bara)
Ans:
The phenomenon of bending of light as it passes from one medium to another is called refraction of light.
Nature of Image formed:
- Image is real.
- Image is inverted and same size.
3)A pencil halfly immersed in water seems bend. Why?
OR
Why does a stick looks curved when it half sinks in a water?
Ans:
A pencil halfly immersed in water seems bend due to refraction of light. When pencil is immersed into water then from evry points of pencil light comes and from water it refracts away from normal so that corresponding image will form at each changed point. Which makes the apperance of bending of pencil or stick.
4)Concave mirror is called converging mirror, why?
Ans:
Concave mirror is called converging mirror because it converges all the parallel rays of light at a point on principal axis when incident on it.
5)Convex mirror is called diverging mirror, why?
Ans:
Conves mirror is called diverging mirror because it diverges all the parallel rays of light away from principal axis when incident on it.
Most
Important Points To Remember:
|
Images formed by Concave Mirror
|
|
S.No
|
Position of the Object
|
Position of the image formed
|
Features/Nature of Image
|
|
|
1
|
When object is kept at infinity
|
Image is formed at focus.
|
Real, Inverted, highly diminished
|
|
|
2
|
When object is kept at beyond C or 2F
|
Image is formed in between 'F' and 'C'
|
Real, Inverted, diminished
|
|
|
3
|
When object is kept at 'C' or '2F'
|
Image is formed at 'C'
|
Real inverted, equal in size
|
|
|
4
|
When object is kept in between 'F' and 'C' or 2F
|
Image is formed beyond 'C'
|
Real, inverted, magnified
|
|
|
5
|
When object is kept at 'F'
|
Image is formed at infinity
|
Real, inverted, highly magnified
|
|
|
6
|
When object is kept in between 'F' and 'P'
|
Image is formed behind the mirror
|
Virtual, erect and magnified
|
|
|
Images formed by Convex Mirror
|
|
1
|
When object is kept at infinity
|
Image is formed at focus to the next side.
|
Virtual, erect and highly diminished
|
|
|
2
|
When an object is kept in between infinity and 'P'
|
Image is formed in between 'F' and 'P' to the next side.
|
Virtual, erect and diminished
|
|
Labels: light, mirror, concave mirror, convex mirror, reflection of light, laws of reflection of light,
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