7th Std Science Term 3 Solution in English | Lesson.2 Universe and Space

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Lesson 2. Universe and Space

Universe and Space Book Back Solution

Lesson 2. Universe and Space

I . Choose the correct answer.

1.  The moon takes _________ days to complete one revolution around the Earth

  1. 25
  2. 26
  3. 27
  4. 28

Ans : 27

2. If the Moon is appeaing in the sky today near the star Karthikai , the position of the Mon after 27 days is near the star

  1. Bharani
  2. Karthikai
  3. Rohini
  4. Asvini

Ans : Karthikai

3.  Telescope was invented by

  1. Han Lippershey
  2. Galilio
  3. Nicolus Coppernicus
  4. Ptolomy

Ans : Han Lippershey

4. The galaxy containing young and hot stars is

  1.  elliptical galaxy
  2. irregular galaxy
  3. cluster
  4. spiral galaxy

Ans : spiral galaxy

5. With the launch of this satellite, ISRO became capable of launching 4 ton heavy satellites.

  1. GSAT- 13
  2. GSAT- 14
  3. GSAT- 17
  4. Way par GSAT- 19

Ans : Way par GSAT- 19

II. Fill in the blanks:

1. Waxing of moon means _________

Ans : changing of Full Moon

2. Heliocentric model is proposed by _________

Ans : Nicolaus Copernicus

3. _________ is the prevailing model of Evolution of the Universe

Ans : Big Bang theory

4. _________ is a large constellation which covers a large part of the sky

Ans : Ursa Major 

5. _________ is the first satellite launched by India

Ans :  Aryabatta

III. Match the following:

1. RohiniGSLV-Mark III
2. GSAT-14GSLV Mark III M1
3. GSAT-19SLV-3
4. Chandrayaan-2PSLV-XL C25
5. MangalyaanGSLV-D5
Ans : 1 – C, 2 – D, 3 – A, 4 – E, 5 – B

IV. True or False – If false give the correct answer:

1. On a full Moon day, when the Sun is setting in the west, Moon rises in the West.

Ans : False

Cu. An. : On a full Moon day, when the Sun is setting in the west, Moon rises in the East.

2. The word crescent refers to the phases where the moon is less than half illuminated.

Ans : True

3. Galilio accepted the Geo-centric model.

Ans : False

Cu. An. : Galilio did not accepted the Geo-centric model.

4. Our Milky Way galaxy is identified as an elliptical galaxy.

Ans : False

Cu. An. : Our Milky Way galaxy is identified as an spiral galaxy.

5. The planet Venus in our solar system doesn’t have a moon.

Ans : True

V. Analogy

1. Older stars : elliptical galaxies :: younger stars : ____________

Ans : Spiral Galaxies

2. Nearest galaxy : Andromeda :: Nearest star : ____________

Ans : Proxima Centauri 

VI. Very short answer:

1. The word ____________ refers to the phases where the Moon is less than half illuminated (cresent / gibbous)

Ans : cresent.

2. ____________ and ____________ planets never appear in the mid-night sky.

Ans : Mercury, Venus.

3. Number of days taken by the Mars to orbit around the Sun.

687 days.

4. In which phase does the size of the planet Venus is small?

When it was in Gibbous phase.

5. The only evidence of the big bang theory is

The only evidence of the big bang theory is a faint glow in space, called cosmic microwave background.

6. The galaxy which contains abundant amount of gas and dust is ____________ ?

Spiral galaxy.

7. Which country launched the world’s first artificial launch vehicle?

Russia launched the world’s first artificial launch vehicle.

VII. Short Answer Questions:

1. What is epicyclic model?

  • To explain the puzzling phenomena astronomers in early times proposed a change in the simple geocentric model. This is called as epicycle model.
  • A small circle whose centre is on the circumference of a larger circle, in ptolemic astronomy.
  • It was seen as the basis of revolution of the seven plants, given a fixed central Earth.

2. Name the four different types of Galaxies.

  • Spiral galaxy.
  • Elliptical galaxy
  • Irregular galaxy
  • Barred spiral galaxy

3. What is constellation?

A constellation is a recognizable pattern of stars in the night sky when viewed from the Earth.

4. Give the expansions of PSLV and GSLV.

  • PSLYV : Polar Satellite Launch Vehicle.
  • GSLYV : Geosynchronous Satellite Launch Vehicle.

VIII. Answer in Detail:

1. Explain the waxing and waning phases in Venus.

Universe and Space Book Back Solution 2021 - 2022

  • As the Venus went around the epicycle, as shown in the diagram Venus would exhibit phases.
  • Also at times the planet would be nearer, making the apparent size grow bigger and at times far making the apparent size smaller
  • If the Venus was going around the Sun, and its orbit is inside that of Earth, Venus would appear when it is near the Earth, it would be brighter and bigger compared to when it is on the other side of the Sun.
  • It can never be seen in the midnight sky. Two
  • Thirdly only if the Venus is revolving around the Sun, it can exhibit gibbous phase, and the size of the gibbous phase smaller than the crescent phase.
  • If the Venus was revolving around the Earth, we can never see the gibbous
    phase of the Venus and it would be seen only if it is orbiting the Sun.

2. Write short notes on constellations.

  • Aconstellation is a recognizable pattern of stars in the night sky when viewed from the Earth.
  • International Astronomical Union has classified 88 constellations to cover the entire celestial sphere.
  • Many of the old constellations have Greek or Latin names and are often named after mythological characters.
  • Ursa Major (Saptha Rishi Mandalam) is a large constellation and it covers a large part of the sky.
  • The most striking feature of this constellation is a group of seven bright stars known as big dipper (seven Sages in Indian astronomy).
  • Ursa Minor in Lattin means ‘the little bear’ it lies in the northern sky.
  • The Pole star — Polaris (Dhrua) lies within this constellation.
  • The main group, ‘little dipper’, consists of seven stars and is quite similar to that found in Ursa Major.

 

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