Chapter- 11
Light, shadows and
refLection
ACTIVITY- 1: To
distinguish transparent, opaque and translucent objects.
Question 1-
Classify different objects depending on whether an object allows light to pass
through it completely, partially or not at all.
Answer- Transparent, translucent and opaque objects.
Question 2-
Classify the objects given in following table as transparent, opaque or
translucent.
|
Object/
Material |
Transparent/
Opaque/ Translucent |
|
Water |
Transparent |
|
Tissue
Paper |
Translucent |
|
Stone |
Opaque |
|
Air |
Transparent |
|
Book |
Opaque |
|
Mirror |
Opaque |
|
Thin
Cloth |
Translucent |
ACTIVITY- 2 : To
show that light travels in a straight line. (Page No.- 109)
Question 1-
Light travels in __________ line path
Answer- Straight.
Question 2-
Light cannot pass through _________ material.
Answer- Opaque.
ACTIVITY- 3: To
show that screen is compulsory for the formation of shadow.
Question 1- For
shadow formation, how many things are required?
Answer- Three i.e. a source of light, an opaque object
and a screen.
Question 2- A
shadow is observed, on a screen, when an ______ object comes in-between screen
and a source of light.
Answer- Opaque.
ACTIVITY- 4: To
study factors on which size and colour of shadow depends.
Question 1- The
size of shadow of a given opaque object depends on relative _____ of source of
light and the opaque object.
Answer- Position.
Question 2-
What may be the colour of opaque object, shadow will always be ________.
(black/ white)
Answer- Black.
ACTIVITY- 5 : To
construct a pinhole camera.
Question 1- Pin
hole camera is based on the fact that in ordinary conditions light travel in ____ path.
Answer- Straight line.
Question 2- The
images formed by pin hole camera is _______ and ________.
Answer- Inverted and smaller in size.
ACTIVITY- 6 : To
observe reflection of lght.
Question 1- A
mirror does not change the direction of light that falls on it. (true/ false)
Answer- False.
Question 2- A
polished or shining surface like plane mirror produces ___________ reflection.
Answer- Regular.
EXERCISE
Question 1- Fill In
The Blanks.
a). An object that allow light to pass through them
partially are known as translucent
objects.
b). Light source like the Sun that emit light of their
own are called luminous
objects.
c). Never ever look directly at the Sun because it
could be extremely dangerous
for the eyes.
d). The change in direction of propagation of light
when light allowed to fall on polished surface is called reflection of light.
e). Due to
reflection phenomena rooms are lighted up in day time though no direct
sunlight enters the room.
Question 2- Write
True Or False.
a). Moon is a luminous object. (False)
b). We can clearly see through transparent material. (True)
c). Shadow of opaque object is always black. (True)
d). Light doesn’t travel in straight line path. (False)
e). Due to reflection of light, rooms are lighted up
during day time though no direct sunlight enters the room. (True)
Question 3- Match
The Column ‘A’ With Column ‘B’.
A B
1. Natural source of light a. Light moves along a straight path (3)
2. CFL, LED and tube light b. Opaque object (5)
3. Rectilinear propagation of light c.
Shadow cast by a heavenly body (4)
4. Eclipse d. Man-made source of light (2)
5. Cardboard, wood and metal e. Sun, stars and firefly (1)
Question 4. Choose
The Correct Answer.
(i). Objects,
like moon, which do not emit light of their own, are called
a) Luminous objects
b) Absorbers of light
c) Non-luminous objects (✓)
d) Reflectors of light
(ii). An
object, through which we can see partially, but not very clearly, is
a) A rubber ball
b) A sheet of plane glass
c) A sheet of tracing paper (✓)
d) A compact disc
(iii). When Sun
(during evening) is behind an object, the size of its shadow in comparison to that of the object
would be
a) Smaller
b) Larger (✓)
c) Almost zero
d) Equal
(iv). The
image, formed by a pin hole camera, is
a) Inverted and diminished (✓)
b) Inverted and enlarged
c) Erect and enlarged
d) Erect and diminished
(v). For shadow
formation, we require :
a) An opaque object
b) A source of light
c) The screen to obtain the shadow
d) All of the above (✓)
Question 5- Very
Short Answer Type Questions.
(i) State the
type of path that light ordinarily follows while going from one point to
another.
Answer- Straight line path.
(ii) Fishes do
not cast shadow in water. Why?
Answer- Due to absence of a screen at proper distance.
(iii) State the
relative position of Sun, Earth and the Moon during solar eclipse.
Answer- During solar eclipse moon is between sun and
earth.
(iv) In a completely dark room,
if you hold a mirror in front of you, will you see a reflection of yourself in the
mirror?
Answer- No.
(v) Two
identical bed sheets, of pink and grey colour are hanging on a rope under the Sun. What would be the
colour of shadow of these two bed sheets?
Answer- Black.
Question 6- Short
Answer Type Questions.
(i) What is
regular reflection?
Answer-When light fall on polished or shining surface
like plane mirror, these surfaces reflect light in a well defined regular
manner, this is called regular reflection. Sometimes regular reflection also
forms images.
(ii) Why shadow
in afternoon is smaller than shadow formed in the morning?
Answer- In afternoon the Sun is above the object, So
forms a smaller shadow. In morning sunlight falls obliquely and forms larger
shadow.
Question 7- Long
Answer Type Questions.
(i) Using
suitable diagrams show that size of shadow formed, depends on relative position of the source of light
and the opaque object.
Answer-
(ii) Using diagram, show the formation of image by
pinhole camera.
Answer-
