CBSE Class 6 - Science - CH 11 - LIGHT, SHADOWS AND REFLECTIONS (#class6Science)(#eduvictors)

LIGHT, SHADOWS AND REFLECTIONS

Umbra and Penumbra
Types of Shadows

NCERT Solution, Q & A

Q1(MCQ): A body which emits light by itself is

(a) Luminous body
(b) Non-luminous body
(c) Shadow
(d) Opaque body

Answer: (a) Luminous body




Q2: Fill in the Blanks
 
(i)  Object like the sun that give out or emit light of their own are called ______________ Object.
(ii)  Light travels in ______________ line.
(iii) _________________ are formed when an opaque object comes in the path of light
(iv) Polished surfaces produce ____________________ reflection which causes glare in our eyes.
(v)  ______________________objects allow light to pass through them completely.
(vi) ______________________ objects do not allow the light to pass through it at all.
(vii) _______________________ objects allow the light to pass through them partially.
(viii) Stars are ________________ sources of light.
(ix) Shadows are of two kinds named _________ and ____________.

Answer:
(i) luminous
(ii) straight
(iii) Shadows
(iv) regular
(v) Transparent
(vi) Opaque
(vii) Translucent
(viii) natural
(ix) umbra, penumbra

Q3(NCERT): Rearrange the boxes given below to make a sentence that helps us understand opaque objects. 

Answer: OPAQUE OBJECTS MAKE SHADOWS


Q4: What are the luminous objects? Give two examples.

Answer: Objects that emit their own light are called luminous objects. Stars, Sun, candle, torch are examples of luminous objects. The light emitted by luminous objects enables us to see things.

Q5: What are non-luminous objects? Give two examples.

Answer: The objects which do not emit light are called non-luminous objects. Table, chair, trees, moon are examples of non-luminous objects.

Q6: To see an object what do we need?

Answer: To see any non-luminous object we need the following:

• source of light
• an object
• eyes

When a light-emitting from luminous body falls on a non-luminous object and is reflected. This reflected light reaches our eyes enables us to see that object.

Q7: Moon appears bright at night. Is it a luminous or non-luminous body?

Answer: Moon is a non-luminous body, it does not emit its own light. It reflects the sunlight that falls on it.

Q8(NCERT): Classify the objects or materials given below 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 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.

Answer:

Object	Transparent /Translucent     /Opaque	Luminous/ Non-luminous
Air, Water	Transparent	Non-luminous
Piece of Rock, Sheet of Aluminium, Mirror, Wooden Board, CD, Umbrella, Wall, Sheet of Carbon Paper, Sheet of cardboard, Moon	Opaque	Non-luminous
A sheet of polythene, Smoke, Fog,  Sheet of cellophone, Wire-mesh,	Translucent	Non-luminous
A piece of Red hot iron, Light fluorescent tube, Lighted torch, Kerosene stove, Sun, firefly	Opaque	Luminous
Flame of gas burner	Translucent	Luminous

Q9: How shadows are formed? What are the different types of shadows?

Answer: When some objects are placed in the path of light, a dark portion is formed on the opposite side of the objects. This dark portion is called a shadow.
There are two types of shadows:

• umbra 
• penumbra.

The umbra is formed where no light reaches and it is a dark, black shadow.
The penumbra is formed where some light reaches and it is grey in colour.

Q10: Do all objects cast shadow?

Answer: No. Only opaque objects cast a shadow.


Q11: Which type of surfaces produce clear images?

Answer: Polished and plane reflecting surfaces produce a clear image.


Q12(NCERT): Can you think of creating a shape that would give a circular shadow if held in one way and a rectangular shadow if held in another way?

Answer: A cylinder object can cast shadows in two ways. When the top circular view faces the sun, a circular shape shadow is formed. When its horizontal side faces the sun, it casts a rectangular shadow.

Q13(NCERT):  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?

Answer: To see the reflection, the source of light is required We can only in the presence of light.

Q14: What is a lateral inversion?

Answer: When an object is placed in front of a plane mirror, the right side of the object appears to be on the left side of the image and left side of the object appears to be on the right side of the image. This is called lateral inversion.


Q15: State the principle behind the working of a pinhole camera.

Answer: Light travels in a straight line. This principle is behind the working of a pinhole camera.


Q16: What are transparent objects?

Answer: The objects which allow light to pass through them are called transparent objects.



Q17: What are opaque objects?

Answer:  The objects which do not allow light to pass through them are called opaque objects.




Q18: What are translucent objects?

Answer: The objects which partially allow light to pass through them are called translucent objects.


Q19: What types of objects do not cast shadows?

Answer: Transparent objects and few translucent objects, because light passes through them.


Q20(MCQ): The image formed in a pinhole camera is
(a) Inverted
(b) Erect
(c) Both a and b
(d) None of the above

Answer: (a) Inverted