Light and Shadow
* Fill in the blanks:
1. An important property of light is that it travels in a straight line.
2. Light can not bend around objects.
3. The two translucent objects are coloured glass and tracing paper.
4. For the formation of shadow, we need source, opaque object and a source of light.
5. Shadows are longest in the morning and in the late afternoon.
Section I
A. Choose the correct option.
1. Natural source of light include
a. sun. [ ]
b. stars. [ ]
c. fires. [ ]
d. all of these. [✓]
2. Which of the following does not allow light to pass through them?
a. Book. [ ]
b. Mirror. [ ]
c. Computer. [ ]
d. All of these. [✓]
3. Which of the following is transparent?
a. glass. [ ]
b. bed. [ ]
c. copy. [ ]
d. none of these. [✓]
4. Light travels in a
a. zigzag path. [ ]
b. straight line. [✓]
c. circular path. [ ]
d. curved line. [ ]
5. The colour of the shadows is
a. red. [ ]
b. orange. [ ]
c. black. [✓]
d. white. [ ]
B. Match the following.
=
|
1.Source of light |
i. Transparent. [3] |
|
2.Translucent |
ii. Shadow. [4] |
|
3.Clean water |
iii. Fixed path of Earth around the sun. [5] |
|
4.Dark patch |
iv. Candle. [1] |
|
5.Orbit |
v. Tracing paper. [2] |
Section II
C. Short answer questions.
1. Define source of light. Name its two types with examples.
= Any object that produces light is called a source of light. Its two types are-
*Natural Source of Light - Sun, Firefly.
*Artificial Source of Light- Candle, torch.
2. Write an important property of light.
= Light travels in a straight line.
3. Why can we see through a glass, but not through a bat?
= Glass is a transparent object. It allows light to pass through it completely. So, we can see through a glass.
On the other hand, bat is an opaque object. It does not allow any light to pass through it. So, we can not see through a bat.
4. Define shadow. What are the conditions required for the formation of a shadow?
= When an opaque object comes in front of the source of light, it blocks the light and forms a dark patch called a shadow.
The conditions for the formation of shadow are -
i. A source of light.
ii. An opaque object.
iii. A source (such as a wall or a screen) on which the shadow would form.
5. Name the two types of movement of Earth.
= Rotation and Revolution.
D. Long answer questions.
1. Define transparent, translucent, and opaque objects.
= The materials which allow light to pass through them completely, are called transparent object. example:- clear water, cellophane, and glass etc.
The materials which allow only some light to pass through them, are called transparent objects. example:- tracing paper and coloured glasses.
The materials which do not allow any light to pass through them, are called opaque objects. example:- book, chair, table etc.
2. Discuss the formation of shadow at different times of the day.
= The sun appears to move across the sky from the morning to the evening. Accordingly, the shape and the length of the shadows change as well. Shadows are longest in the morning and in the late afternoon. They are shortest at noon when the sun is overhead.
3. How is day and night caused? Explain.
= The rotation of earth causes the formation of day and night. As earth rotates, one half of it faces the sun. This part of earth gets light from the sun and has day. The other half of earth faces away from the sun and has night. India and United States of America(USA) are located on the two opposite halves of earth. So, when India faces the sun and has day, the USA faces away from the sun and has night. Similarly, when India has night, the USA has day.
4. Define solar eclipse. How it is formed?
= A solar eclipse occurs when the moon comes between the sun and earth such that the shadow of the moon is cast on earth. During a solar eclipse, the moon hides the sun from the earth either partially or totally.
A solar eclipse can be of the following two types-
*Total Solar Eclipse:- A total solar eclipse occurs when the sun is totally hidden by the moon.
*Partial Solar Eclipse:- A partial solar eclipse occurs when only a portion of the sun is hidden by the moon.