Class 7 Basic Science Chapter 8 Question Answer Notes Wonders of Sky

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Wonders of Sky Class 7 Questions and Answers Notes

Class 7 Basic Science Chapter 8 Wonders of Sky Question Answer Pdf

Basic Science Class 7 Chapter 8 Question Answer Kerala Syllabus

Let Us Assess

Question 1.
Observe the picture. Check the orbital path of the Moon around the Earth and complete the table below:

Answer:
The starting position of the lunar eclipse B
The position of complete lunar eclipse C
The position where the lunar eclipse ends D

Question 2.
Observe the picture and complete the table by matching the boxes appropriately.

Answer:

Question 3.
Some statements are given below. Tick (✔) the correct ones.
• A Full Moon is the day when the part of the Moon on which the sunlight falls, is completely visible from the Earth.
• The waxing crescent Moon is visible overhead at sunset.
• The period of revolution of the Moon and the period during waxing will be visible are the same.
• Solar eclipse occurs only on New Moon day.
• Lunar eclipse occurs only on Full Moon day.
• Lunar eclipse occurs on all Full Moon days.
Answer:

• A Full Moon is the day when the part of the Moon on which the sunlight falls, is completely visible from the Earth.
• Solar eclipse occurs only on New Moon day.
• Lunar eclipse occurs only on Full Moon day.

Class 7 Basic Science Chapter 8 Extended Activities Answers

Question 1.
Let’s do an activity to find out how Solar Eclipse occurs.
Preparation
Place a football on a table.
Let a child stand facing the table at a distance of one and a half meters.
Let the child hold a small ball fixed on a stick as shown in the picture.
Close one eye and hold the small ball closely in front of the other eye and look at the football on the table.

a) Is the football the only thing to disappear from the view?
b) Slowly move the small ball forward aw ay from the eye. What change occurs in viewing the ball?
c) How far should the small ball be held from the eye for the football to be completely hidden? If the small ball is further moved aw ay from the eye, w hat change can be observed in the hidden football?
d) How should you hold the small ball to hide the football partially?

e) Compare the observations you had during the above experiment with the different pictures

Answer:
In the activity:

• Football: Represents the Sun.
• Small ball: Represents the Moon.

a) No. When the small ball (Moon) is held close to the eye (Earth), it blocks not only the football (Sun) but also the area around it.

b) As the small ball (Moon) moves away from the eye (Earth), the area it blocks becomes smaller. The football (Sun) may still be partially hidden, but more of its surroundings can be seen.

c) The small ball (Moon) needs to be held at a specific distance from the eye (Earth) to block the football (Sun) completely. This distance is determined by the relative sizes of the football and the small ball. If the small ball is moved further away, the football will no longer be completely hidden, and part of it will be visible.

d) To partially hide the football (Sun), the small ball (Moon) should be positioned so that it only partially covers the football.

e) The provided images depict three different phases of a solar eclipse:
Total Eclipse: The Moon completely covers the Sun, leaving only the Sun’s outer atmosphere visible.
Annular Eclipse: The Moon is slightly smaller than the Sun, leaving a ring of sunlight around the Moon’s silhouette.
Partial Eclipse: Only part of the Sun is covered by the Moon.
Here’s a comparison of the activity’s observations and the eclipse images:

Question 2.
What are India’s achievements in Space Science? Collect information and prepare an article. Conduct a seminar exploring the ICT possibilities.
Answer:
India’s Space Achievements:

• Launched numerous satellites.
• Explored the Moon and Mars.
• Developed reliable launch vehicles.
• Created navigation system NavIC.
• Applied space technology to various sectors.
• ICT Possibilities:
• Satellite communication.
• Remote sensing.
• Navigation.
• Data analysis.
• Education and research.

Class 7 Basic Science Chapter 8 Intext Question and Answers

Question 1.
You might have seen your own shadow. How is it formed?
Answer:
A shadow is formed when an object blocks light from reaching a surface, and your shadow is formed because your body is opaque and doesn’t allow light to pass through it.

Question 2.
Observe the picture.

a) In which direction will the shadow of the tree be seen in the morning?
Answer:
The shadow of a tree in the morning will be long and point west.

b) In which direction will the shadow of this tree be in the evening?
Answer:
The shadow of a tree in the evening will be long and point east.

c) What change can you see in it at noon?
Answer:
The shadow of a tree at noon will be short because the sun is directly overhead, and its rays fall vertically on the tree.

Question 3.
Observe the changes in the size and the direction of the shadow of the tree in the above situations. Record it in your Science Diary.
Answer:
The size and direction of a tree’s shadow change throughout the day because the sun’s position changes in the sky:

• Morning: Shadows are longer and point west. This is because the sun rises in the east.
• Noon: Shadows are shorter because the sun is directly above the tree.
• Afternoon: Shadows are shorter and point east. This is because the sun sets in the west.

Question 4.
Let’s do a simple experiment.

Hold a bangle as shown in the figure 1. Light a torch against it. Observe the shape of the shadow formed on the wall.
Hold a bangle as shown in the figures 2 and 3. Repeat the process. Are the shapes of all the three shadows the same?
Answer:
If you hold a bangle, as shown in Figure 1, and shine a torch against it, the shadow formed on the wall will likely be a crescent shape. This phenomenon occurs because the light from the torch is blocked by the curved surface of the bangle, creating a curved shadow.
Figure 2 and Figure 3 show the hand and bangle in slightly different positions, but the basic idea is still the same: the bangle’s curved surface stops light from the torch, making a crescent-shaped shadow.

Question 5.
Repeat the experiment using the following objects given in the Science Kit.
Materials: Pen, cricket ball, piece of glass, instrument box, plate, steel glass, football. Hold each object against the wall in different ways and light the torch onto them. Tabulate your observations.

Answer:

Question 6.
Analyse the table
a) Do all the objects cast shadows?
Answer:
No, If the glass is transparent, no shadow is formed. If it is opaque, the shadow will be irregular depending on the object’s shape.

b) On which side of the source of light is the shadow formed?
Answer:
Shadow forms in the direction opposite to that of the source of light.

c) Which were the objects that always formed shadow of the same shape?
Answer:
Only spherical objects always form circular shadows.

Question 7.
The Earth, the Moon and other celestial bodies are opaque objects. Do they form shadows?
Answer:
Yes, they do form shadows.
We have learnt that the Sun, a source of light, is very large and that the Earth is relatively small in size. Observe the ray diagram of the sunlight reaching the Earth.

The Earth does not allow sunlight to pass through it. Hence shadow is formed on the other side.

Question 8.
Observe the shaded part A in figure 4, in which the shadow of the Earth is formed. Look at the shape of the Earth’s shadow. Doesn’t it look like a cone ice cream cup?
Answer:
Yes, it has the shape of a cone ice cream cup.

Question 9.
What are the facts you have understood about the Earth’s shadow?
Answer:

• Being an opaque object, the Earth forms its shadow.
• The shadow of the Earth is always formed in the direction opposite to the Sun.
• The Earth’s shadow gradually diminishes and finally disappears as it moves away.

Question 10.
You have now understood the shape of the shadow of the Earth. Guess whether it will be day or night where the Earth’s shadow is formed. Write it down.
Answer:
Earth’s shadow has the shape of a cone ice cream cup. So, the place where Earth’s shadow is formed is night.

Question 11.
Observe the picture.

a) Are all celestial bodies of the same size?
Answer:
No
The size of the shadows varies with the change in the size of the celestial bodies.

b) Doesn’t the moon also cast a shadow like this?
Answer:
Yes.
In a celestial sphere, it is day where the light falls and night where the shadow is formed.

Question 12.
Among the following, which is the probable position of the moon in the shadow of the earth?

Discuss and record your answer in the Science Diary.
Answer:
The probable position of the Moon in the shadow of the Earth is behind the Earth.
This is because the Earth’s shadow is cast away from the Sun. If the Moon were in front of the Earth, it would not be in the shadow. Therefore, the Moon must be behind the Earth to be in its shadow. This is illustrated in Figure B.

Question 13.
The figure below shows the celestial spheres the Sun and the Earth and the Moon’s orbit. B, C and D are the various positions in the path through which the Moon revolves round the Earth.

a) At which of these positions does the Moon enter the Earth’s shadow?
Answer:
B

b) At what position does the Moon enter completely in the Earth’s shadow?
Answer:
C

c) At which point does the Moon come out of the Earth’s shadow?
Answer:
D

Question 14.
In the above picture, the part of the Moon where sunlight falls is facing the Earth. On this day, the Moon can be seen from the Earth. But w hen you reach position C, you cannot see the Moon. Why? Isn’t it because the Moon comes in the shadow of the Earth?
Answer:
When the Moon is at position C, it is indeed in the Earth’s shadow. This is why it becomes invisible from Earth.
The Earth’s shadow is cast away from the Sun, and as the Moon orbits the Earth, it can pass through this shadow. When it does, it is eclipsed and cannot be seen from Earth. This phenomenon is known as a lunar eclipse.

Lunar eclipse is one of the most beautiful phenomena visible in the sky. During a total eclipse, the Moon appears dim in orangish red colour. Remember to observe the upcoming lunar eclipse without fail.

Question 15.
What happens when the Moon comes in a straight line between the Sun and the Earth? The Moon is a smaller sphere than the Earth. Can the shadow of the Moon completely cover the Earth? Observe the picture and record your inference in the Science Diary.

Answer:
The Moon’s shadow does not completely cover the Earth. The Sun cannot be seen at that time because the Moon is covering the Sun. People in the area where the Moon’s shadow falls cannot see the Sun because the Moon covers the Sun.

Now you might have understood that the Moon’s shadow does not completely cover the Earth. Can those people, on the side in which the Moon’s shadow falls on the Earth see the Sun at that time? The Sun cannot be seen at that time because the Moon is covering the Sun. This is solar eclipse. Does this phenomenon occur during the day or at night? Analyse the figure, arrive at an inference and discuss in the class.

Question 16.
Look at the pictures of different solar eclipses.

We can observe total solar eclipse, annular solar eclipse and partial solar eclipse. Analyse the above pictures. Discuss their characteristics and record them in the Science Diary.
Answer:
Total Solar Eclipse:

• The Moon completely blocks the Sun, creating total darkness in the area of the eclipse.
• Daytime turns into night for a brief period.

Annular Solar Eclipse:

• The Moon is slightly smaller than the Sun, leaving a ring of sunlight visible around the Moon.
• Daytime remains bright, but there is a noticeable dimming of the sunlight.

Partial Solar Eclipse:

• The Moon partially covers the Sun, creating a crescent-shaped solar disk.
• The amount of sunlight blocked varies depending on the position of the Moon.
• Daytime remains partially bright.

Question 17.
You might have noticed the news related to the solar eclipse in newspapers. Places suitable for observing solar eclipse and the precautions to be taken usually appear in the news. How can we observe a solar eclipse safely? Read the following note and write down your findings in Science Diary.
Answer:
Direct observation of a solar eclipse can be harmful to the eyes. This is because intense sunlight can damage the retina, a sensitive part of the eye. Therefore, it is essential to use proper filters or indirect methods to observe a solar eclipse.
Safe methods for observing a solar eclipse include:

• Using solar eclipse glasses: These special glasses have a special filter that blocks harmful ultraviolet and infrared rays while allowing visible light to pass through.
• Using a solar filter for telescopes or binoculars: A solar filter should be attached to the front Of the telescope or binoculars to protect your eyes.
• Projecting the Sun’s image: You can project the Sun’s image onto a screen using a pinhole camera or a telescope. This indirect method allows you to observe the eclipse without looking directly at the Sun.

It is important to avoid using:

• Homemade filters: These filters may not provide adequate protection and can be dangerous.
• Sunglasses: Sunglasses do not block harmful ultraviolet or infrared rays and should not be used to observe a solar eclipse.
  X-ray film: X-ray film can be harmful to your eyes and should not be used.

Question 18.
How is it possible for the Moon to shine so brightly, when it can’t shine by itself? Observe the image.

What would be the reason for the brightness of the moon?
Answer:
The Moon shines because it reflects sunlight. It’s like a mirror in space, reflecting the light from the Sun back to Earth. That’s why we see it as a bright object in the night sky.

Question 19.
In the picture given below, can’t you see the sunlight falling simultaneously on the Earth and the Moon? Since these are opaque objects, won’t the light be reflected?

Answer:
In the picture, sunlight is falling on both the Earth and the Moon. Both of these objects are opaque, meaning they don’t allow light to pass through them. The Moon is too small to cast a shadow that covers the whole Earth. Even when it’s between the Sun and Earth, its shadow only covers a small part. That’s why we don’t always see a solar eclipse everywhere on Earth.

Question 20.
Moonlight is sunlight reflected from the Moon. The surface of the Moon is rough. If so, is it due to regular or irregular reflection? Discuss and write it down in your Science Diary.
Answer:
The surface of the Moon is rough, and this roughness causes the sunlight to be irregularly reflected. This means that the light is scattered in many different directions, rather than being reflected in a single, focused beam. Because of this irregular reflection, the Moon appears to have a soft, diffuse glow in the night sky.

Question 21.
Observe the shape of the Moon on different days and draw them in the Science Diary.
Answer:
Here are some tips that you can use while drawing.

1. Choose a starting date: Decide on a day to begin your moon observations.
2. Observe the moon: Look at the moon each night at the same time. Pay attention to its shape and brightness.
3. Draw the moon: In your science diary, draw the moon as accurately as possible. Label the date and time of your observation.
4. Continue observing: Repeat steps 2 and 3 for several weeks.
5. Analyse your drawings: Compare the moon’s shape on different days. Notice how it changes over time.

Question 22.
Why is the spherical Moon seen in different shapes on different days?
Answer:
The Moon appears in different shapes throughout the month because of its orbit around the Earth. As the Moon orbits, the amount of its illuminated surface that we can see from Earth changes.

Question 23.
Let’s do an activity.
Materials needed: Three smiley balls, black paint
Examine the pictures and notes in the boxes given below. Paint half of each smiley ball with black paint as suggested in the notes in the boxes.

The black painted part represents the shadow side of the Moon. The unpainted part represents that part of the Moon where light falls.
Place the balls in the class in east-west direction as shown in the picture below.

The unpainted part of the smiley ball should face the light and the black painted part should face the side opposite of light. Imagine the smiley ball as the Moon and the bulb as the Sun. A, B and C are the positions when the Moon revolves around the Earth.
The child should sit in the middle of balls A and C and observe. As per the picture, how will the child be viewing all the three balls?
a) On which ball can the child see the shadow portion completely? ( )
Answer:
A

b) Ball placed at which position enables the child to view half illuminated and half shadow portions? ( )
Answer:
B

c) On which ball can the child see the illuminated portion completely? ( )
Answer:
C

Question 24.
Given below are the positions and shapes in which a child observed the Moon in the sky after sunset on different days. Analyse the given picture based on the activity you have done.

Doesn’t the illuminated part of the Moon viewed from the Earth show a difference at each position? Examine the table given below and record your inferences in your Science Diary.

Answer:
The illuminated portion of the Moon, when viewed from Earth, shows differences at each position. At position D The shadow side completely faces the Earth so that we cannot see the Moon. At position E, only half of the Moon is visible because half the illuminated and half the shadow sides face the Earth. Coming to position F Moon is completely visible as the illuminated side is completely facing the Earth.

Question 25.
Observe the pictures given below.
The two pictures A and B represent the revolution of the Moon from New Moon to Full Moon and vice versa. Are both the pictures alike? What differences can you observe in these pictures?

a) Which picture shows the illuminated portion of the Moon getting increased, when viewed from the Earth? ( )
Answer:
Picture A
b) Which picture shows the illuminated portion of the Moon getting decreased, when viewed from the Earth? ( )
Answer:
Picture B

Question 26.
Observe the given calendar.
Don’t you see these symbols in the calendar? By looking at the calendar, can you find out how many days it takes for the Moon to reach the New Moon from Full Moon?

Answer:

Question 27.
Examine the next month’s calendar also. Find out how many days are needed for the Moon to reach the next New Moon from the Full Moon?

Didn’t It take 30 days for one New Moon to reach the next?

Answer:
Yes.

Question 28.
The Moon takes 27\(\frac{1}{3}\) days to revolve round the Earth once. What is the reason for this difference? Discuss.
Answer:
The Earth needs 365\(\frac{1}{2}\) days to revolve around the Sun once. 8v the time the Moon revolves around the Earth once, the Earth would have travelled some distance in its orbit with the Moon around the Sun. Thus, a change occurs to the position of the Earth. Hence the Moon will have to travel some more distance in the same path to repeatedly see the phases of the Moon. It takes more than two days for this. That is why it takes 29\(\frac{1}{2}\) days from one New Moon to the next New Moon.

Question 29.
We have searched the reasons for the beautiful sights of the sky. Find out the New Moon and Full Moon days in this month’s calendar and observe the Moon every day after the sunset from New Moon to Full Moon. Share your findings with your friends.
Answer:
The New Moon and Full Moon days for September 2024 are:

• New Moon: September 2, 2024
• Full Moon: September 18, 2024

Here are some things you might observe as you watch the Moon:

• The Moon’s brightness: The Móon’s brightness varies depending on its phase. It is brightest when it is Full Moon and dimmest when it is New Moon.
• The Moon’s position in the sky: The Moon’s position in the sky changes each night. It rises earlier and sets later as it moves from New Moon to Full Moon.

Wonders of Sky Class 7 Notes Extra Questions and Answers

Question 1.
How is a shadow formed?
Answer:
A shadow is formed when an object blocks light from reaching a surface.

Question 2.
What are the different types of solar eclipses?
Answer:
Total solar eclipse, annular solar eclipse, and partial solar eclipse.

Question 3.
What is Lunar Eclipse?
Answer:
As the Moon revolves round the Earth, the Earth sometimes comes between the Sun and the Moon in a straight line. At this time, the Moon will be in the shadow of the Earth. This is the lunar eclipse.

Question 4.
A lunar eclipse can be observed directly. However, observing the solar eclipse directly is harmful to the eyes. Why?
Answer:
Observing a lunar eclipse directly is generally safe because the Moon reflects sunlight. It’s like looking at the moon on any other night. The light is significantly less intense and doesn’t pose a risk to your eyes. However, observing a solar eclipse directly is extremely harmful. Even during the partial phases of a solar eclipse, the Sun’s intense light can damage your retinas, the light-sensitive tissue at the back of your eyes. This damage can lead to permanent vision loss.

Question 5.
You are provided with some of the objects that are given below.
Light a torch against each of the objects. Observe the shape of the shadow formed on the wall.
A) Classify the given objects into two as given below.

B) Write the result that helped you to classify the objects.
Answer:
A)

Objects that form circular Shadow	Objects that do not form circular Shadow
Football Cricket ball Smiley ball	Pen Instrument box Plate Steel glass

B) Only spherical objects always form circular shadows.

Question 6.
Observe the ray diagram of the sunlight reaching the Earth.

A) Are there any shadows formed?
B) What is the shape of the Earth’s shadow?
C) Write any three facts about Earth’s shadow.
Answer:
A) The Earth does not allow sunlight to pass through it. Hence shadow is formed on the other side.
B) Shape of a cone ice cream cup.
C)

• Being an opaque object, the Earth forms its shadow.
• The shadow of the Earth is always formed in the direction opposite to the Sun.
• The Earth’s shadow gradually diminishes and finally disappears as it moves away.

Question 7.
Observe the news report.

A) Draw a circle to represent the Sun.
Draw a smaller circle to represent the Moon.
Position the Moon between the Sun and the Earth.
Draw the shadow cast by the Moon onto the Earth.
Label the Sun, Moon, Earth, and shadow in your drawing.
B) Explain what happens during a solar eclipse based on your diagram.
C) What are the risks of looking directly at a solar eclipse? Describe atleast two safe ways to observe a solar eclipse.
Answer:

B) In a solar eclipse, the Moon passes between the Sun and the Earth. When this happens, the Moon blocks the Sun’s light, casting a shadow onto the Earth. The area of the Earth that is covered by the shadow experiences a solar eclipse.

C) Direct observation of a solar eclipse can be harmful to the eyes. This is because intense sunlight can damage the retina, a sensitive part of the eye. Therefore, it is essential to use proper filters or indirect methods to observe a solar eclipse.

Safe methods for observing a solar eclipse include:

• Using solar eclipse glasses: These special glasses have a special filter that blocks harmful ultraviolet and infrared rays while allowing visible light to pass through.
• Using a solar filter for telescopes or binoculars: A solar filter should be attached to the front of the telescope or binoculars to protect your eyes.

Question 8.
What do you mean by New Moon?
Answer:
New Moon occurs when the shadow side of the Moon completely faces the Earth. We cannot see the Moon on this day.

Question 9.
Why does the Moon appear in different shapes throughout the month?
Answer:
The Moon’s orbit around the Earth changes the amount of its illuminated surface that we can see.

Question 10.
How long does it take for the Moon to revolve around the Earth once?
Answer:
Approximately 27\(\frac{1}{3}\) days.

Question 11.
Why does it take more than 27\(\frac{1}{3}\) days for the Moon to go from one New Moon to the next?
Answer:
The Earth’s orbit around the Sun affects the Moon’s position, so it takes slightly longer for the Moon to return to the same position relative to the Sun.

Question 12.
Observe the Sun, the Earth and the Moon in the given illustration.

A) What do pictures 1 & 5 indicate? Write the reason for seeing them like this.
B) Waxing and waning happens on the moon. Why?
Answer:
A) Picture 1 indicates a new moon day, and picture 5 indicates a full moon day. When the moon comes to position 1, The lighted part of the moon is not facing the Earth, so the moon is not visible. When the moon comes to position 5, the whole of the lighted part of the Moon is facing the Earth.

B) From the new moon day to the full moon day, the lighted portion of the moon becomes more visible. This is called waxing. From the full moon day to the new moon day, there is a decrease in the visibility of the lighted area of the moon from the Earth. This is called waning. The difference in the visibility of the lighted and dark areas of the moon when observed from the Earth is the reason for the waxing and waning of the moon.

Question 13.
Choose the incorrect statements from the following and correct them.
a) Only one side of the moon always faces the Earth.
b) On a new moon day, the lighted part of the moon faces the Earth.
c) Waxing is the decrease in visibility of the lighted area of the moon on the earth from the full moon day to the new moon day.
d) Since the moon revolves around the earth, the position of the moon in the sky changes.
Answer:
b) and c) are the incorrect statements.
The corrected statements are
b) On a new moon day, the lighted part of the moon is not facing the earth.
c) Waxing is the increase in visibility of the lighted area of the moon on the earth from the new
moon day to the full moon day.

Question 14.
Observe the figure. Different positions of the moon in its path of revolution around the earth are depicted here.

A) Match the facts given below by drawing lines.

B) Vani observed the moon from the full moon day to the new moon day. Is there a decrease or increase in the visibility of the lighted area of the moon? What is it called?
C) What do you mean by waxing of the moon?
Answer:

B) There is a decrease in the visibility of the lighted area of the moon from the Earth. It is called the waning of the moon.
C) From the new moon day to the full moon day lighted portion of the moon becomes more visible is called the waxing of the moon.

Wonders of Sky Class 7 Notes

• All opaque objects form shadows.
• Shadow forms in the direction opposite to that of the source of light.
• Only spherical objects always form circular shadows.
• As the Moon revolves round the Earth, the Earth sometimes comes between the Sun and the Moon in a straight line.
• At this time the Moon will be in the shadow of the Earth.
• When the Moon revolves round the Earth, the Moon rarely comes in between the Earth and the Sun in a straight line.
• At this time the Moon’s shadow falls on the Earth.
• People in the area where the Moon’s shadow falls cannot see the Sun because the Moon covers the Sun. This is solar eclipse.
• A solar eclipse is visible only to those in the lunar shadow.
• The sunlight falling on the Moon’s surface gets scattered and reaches the Earth. This is the moonlight that we see at night.
• New Moon occurs when the shadow side of the Moon completely faces the Earth. We cannot see the Moon on this day.
• Full Moon occurs when the illuminated part of the Moon completely faces the Earth.
• Half Moon is seen when the half illuminated and half shadow portions of the Moon face the Earth.
• When viewed from the Earth, the illuminated part of the Moon keeps on increasing from the New Moon to Full Moon. This period is known as the waxing or white halo.
• When viewed from the Earth, the illuminated part of the Moon keeps on decreasing from the Full Moon to New Moon. This period is known as the waning or black halo.
• It takes 29\(\frac{1}{2}\) days from one New Moon to the next New Moon.