# Kerala Syllabus 10th Standard Social Science Important Questions Chapter 1 Seasons and Time

## Kerala State Syllabus 10th Standard Social Science Important Questions Chapter 1 Seasons and Time

Question 1.
Which of the following is summer solstice in Northern Hemisphere?
March 21
September 23
June 21
December 22
June 21

Question 2.
The northward apparent movement of the sun from Tropic of Capricorn to Tropic of Cancer
Utharayanam
Dakshinayanam
Solstice
Equinox
Utharayanam

Question 3.
The season that marks the transition from the severity of summer towards winter.
Spring season
Rainy season
Autumn season
Winter season
Autumn season

Question 4.
Which of the following is equinox?
September 23
December 22
June 21
July 14
September 23

Question 5.
Based on the differences in the atmospheric conditions, the season experienced in India in the months of March and April.
Autumn
Spring
Summer
Winter
Spring

Question 6.
When the sun is in the Northern Hemisphere, what will be the condition of 90°S?
6 months of day
1 month of night
24 hours of night
6 months of night
6 months of night

Question 7.
What will be the Indian Standard Time when it is 8 a.m. on Sunday at Greenwich?
Monday 12.30 pm
Sunday 12.30 pm
Sunday 1.30 pm
Sunday 2.30 pm
Sunday 1.30 pm

Question 1.
What is meant by seasonal change?
The earth experiences the recurrence of winter, summer and the rainy season one after the other.
Such a change on the earth is known as seasonal change.

Question 2.
What is revolution?
The earth revolves around the sun in an elliptical orbit. This motion which takes one year is known as revolution.

Question 3.
How much time does the earth take to complete one revolution?
The earth takes 365 days, 5 hours, 48 minutes and 45 seconds to complete one revolution (365 $$\frac { 1 }{ 4 }$$ days).

Question 4.
Which is the standard meridian of India based for calculating time?
82 $$\frac { 1 }{ 2 }$$° E longitude

Question 5.
Which season is experienced in Southern Hemisphere when it is spring in the Northern Hemisphere?

• Southern Hemisphere experiences autumn.
• Similarly, when it is spring in the Southern Hemisphere, it is autumn in the Northern Hemisphere.

Question 6.
Why is zero degree longitude known as the. Greenwich meridian?
It acquires its name from Greenwich, the place where the Royal British Observatory is situated and through which this line passes.

Answer the following. Score 2 each.

Question 1.
What are the reasons for the occurrence of different seasons?

• Revolution of the earth
• Tilt of the earth’s axis
• Parallelism of the earth’s axis
• The apparent movement of the sun.

Question 2.
What is the Greenwich Mean Time when the Indian Standard Time is 1 p.m on Sunday?
The time difference between India and Greenwich is 514 hours. The Greenwich time will be 7.30 a.m on Sunday. (1p.m – 5 $$\frac { 1 }{ 2 }$$ hours = 7.30 am)

Question 3.
What is the tilt of the earth’s axis at vertical plane and horizontal plane?

• At vertical plane, tilt of the earth’s axis is 23 $$\frac { 1 }{ 2 }$$°
• At horizontal plane, the tilt is 66°.

Question 4.
What is known as parallelism of the earth’s axis?
The axis of the earth is tilted at an angle of 66 $$\frac { 1 }{ 2 }$$° from the orbital plane and 23 $$\frac { 1 }{ 2 }$$° from the vertical plane. The earth maintains this tilt throughout its revolution. This is known as parallelism of the earth’s axis.

Question 5.
How does the tilt of earth’s axis influence the change of seasons?
If the earth’s axis is not tilted, the sun’s position will have been over the equator always. If so, both the hemispheres would receive equal amount of sunlight. There wouldn’t have been change of seasons on earth. Since the tilt is maintained throughout the revolution, the position of the sun in relation to the earth varies. The sun shifts apparently between Tropic of Cancer and Tropic of Capricorn and this results in seasons.

Question 6.
What is meant by apparent movement of the sun? Name the two latitudinal lines that gain importance in this process.
Since the parallelism of the earth’s axis is maintained same throughout the revolution, the position of the sun in relation to the earth varies apparently between Tropic of Cancer and Tropic of Capricorn. This is known as the apparent movement of the sun.
The movement of the sun is in between 23 $$\frac { 1 }{ 2 }$$° N and 23 $$\frac { 1 }{ 2 }$$° S.

Question 7.
What are equinoxes?
March 21 and September 23 are equinoxes. On these days, the sun is vertically over the equator. Both the hemispheres receive equal amount of sunlight. Hence the length of day and night will be equal on these days in both the hemispheres.

Question 8.
Answer the question based on the table.

 Relative position of the sun Northern Hemisphere Southern Hemisphere March 21 to September 23 September 23 to March 21

a. What will be the season in Southern Hemisphere when it is summer in Northern Hemisphere?
b. What will be the season in Northern Hemisphere when it is summer in Southern Hemisphere?
a. Winter season in Southern Hemisphere.
b. Winter season in Northern Hemisphere. Reason: The hemisphere in which the sun is located receives more heat.

Question 9.
Complete the table.

 Months Seasons in Northern Hemisphere A. October-November …………………………… B. March-April …………………………… C. January – February …………………………… D. May-June ……………………………

Hints:

• Spring season
• Summer season
• Autumn season
• Winter season

A. Autumn season
B. Spring season
C. Winter season
D. Summer season

Question 10.
When Northern Hemisphere has the following seasons, which are the seasons experienced in the Southern Hemisphere?

• Summer
• Spring
• Winter
• Autumn

 Northern Hemisphere Southern Hemisphere Summer Winter Winter Summer Spring Autumn Autumn Spring

Question 11.
a. The season that marks the transition from summer to winier
b. The season that marks the transition from winter to summer
a. Autumn
b. Spring

Question 12.
The duration of days and nights at each place on the earth is not the same throughout the year. Why?

• Rotation and occurrence of day and night.
• Tilt of the earth’s axis and revolution.

Question 13.
How many time zones are there? What is the time/degree difference between each zone?

• Based on the Greenwich line, the world is divided into 24 time zones, each with a time difference of one hour.
• The longitudinal extent of each time zone is 15°.

Question 14.
Writes noies on
Greenwich line
Greenwich Mean Time
OR
Write the sign if chance of Greenwich meridian
or
Q° longitude line in determining time.

• The zero degree longitude is known as Greenwich line. Time is calculated worldwide based on the Greenwich line. Hence this line is also known as prime meridian.
• Based on the Greenwich line, the world is divided into 24 time zones. The local time at the Greenwich line is known Greenwich Mean Time.

Question 15.
How are the standard meridian and standard time calculated by each country?
OR
Every country considers a particular longitude as their standard meridian for determining time. Why?
The local time would be different at each longitude. If we start calculating the local time at different places based on the longitude there, it would create lot of confusion. So each country in the world considers the longitude that passes almost through its middle as the standard meridian.
The local time at the standard meridian is the standard time of the country.

Question 16.
Which longitude is considered as the standard meridian of India? Why is it considered so?
82$$\frac { 1 }{ 2 }$$°E longitude is considered as the standard meridian of India. The line passes almost through the middle of India.
Each country in the world considers the longitude that passes almost through its middle as the standard meridian. The longitudinal extent of India is from 68°E to 97°E. This amounts roughly to 30°.

The 82$$\frac { 1 }{ 2 }$$°E longitude passes almost through the middle of these longitudes. So 82$$\frac { 1 }{ 2 }$$°E longitude is considered as the standard meridian of India.

Question 17.
What is known as Indian Standard Time? How does it differ from Greenwich Time?

• 82$$\frac { 1 }{ 2 }$$°E longitude is the standard meridian of India. The local time of this longitude is generally considered as the common time of India. This is known as Indian Standard Time.
• The IST is 5$$\frac { 1 }{ 2 }$$ hours ahead of Greenwich time.

Question 18.
Land areas through which the 180° longitude passes are avoided. Why? Based on the Greenwich line, the world is ;
The west and east of 180° longitude line records two different times with 24 hours difference. This creates much difficulties. So land areas along the 1800 longitude are avoided and the longitude passes through ocean.

Question 19.
Arrange the columns suitably.

 A B Greenwich line Local time international Dale Line Prime meridian Indian Standard Time 180° Apex position of the sun 82 $$\frac { 1 }{ 2 }$$ °E

 A B Greenwich line Prime meridian international Dale Line 180° Indian Standard Time 82 $$\frac { 1 }{ 2 }$$ °E Apex position of the sun Local time

Question 20.
Identify the longitude by examining the time difference.
The time at A is 10 pm Sunday. A is situated at 150° W to Greenwich. At the same time, it is 3 pm Monday at B. If so, find the longitude at which B is situated.
a. At 75° E of Greenwich
b. At 120° W of Greenwich
c. At 90° W of Greenwich
d. At 105° E of Greenwich
d. At 105° E of Greenwich

Question 21.
Identify the wrong statement from the following and rewrite it correctly.
A. The duration of day in the Southern Hemisphere increases from September 23 to December 22.
B. The duration of night in the Southern Hemisphere increases from September 23 to December 22.
C. The duration of day in the Northern Hemisphere increases from March 21 to June 21.
D. The duration of night in the Northern Hemisphere decreases from March 21 to June 21.
The wrong statement is B.
The duration of night in the Southern Hemisphere decreases from Septembers 23 to December 22.

Question 22.
The seasons experienced in the Southern Hemisphere are given in the table. Write down the corresponding seasons in the Northern Hemisphere.

 Months Seasons (Southern Hemisphere) March 21 to June 21 Autumn June 21 to September 23 Winter September 23 to December 22 Spring December 22 to March 21 Summer

 Months Seasons (Southern Hemisphere) March 21 to June 21 Spring June 21 to September 23 Summer September 23 to December 22 Autumn December 22 to March 21 Winter

Question 23.
The time of sunset varies over different months. Why?
The apparent movement of sun between the Tropic of Cancer and the Tropic of Capricorn is the reason.
When the sun is over the northern hemisphere, longer days and shorter nights are experienced here.

When the sun is over the southern hemisphere, the northern hemisphere experiences shorter days and longer nights. This causes variations in the time of sunrise and sunset.

Question 24.
There is an increase of time towards the east and decrease in time towards the west of zero degree longitude. Why?

• The earth rotates from west to east. So the sun rises in the east and sets in the west.
• Hence there is an increase in time towards the east and decrease in time towards the west.

Answer the following. Score 3 each.

Question 1.
Which are the equinox days? Write the peculiarities of these days?
OR
Write the peculiarities of the days March 21 and September 23 based on the apparent position of the sun.

• The equinox days are March 21 and September 23.
• The apparent position of the sun on these days would be over the equator.
• Equal amount of sunlight is received in the northern as well as the southern hemispheres when the sun is vertically over the equator.
• Hence the length of day and night will be equal on these days in both the hemispheres.

Question 2.
Write the peculiarities of day and night on June 21 and December 22 in both the north and south hemispheres.
June 21

• Known as summer solstice in Northern Hemisphere.
• The longest day and the shortest night in the Northern Hemisphere.
• The longest night and the shortest day in the Southern Hemisphere.

December 22

• Known as winter solstice in Northern Hemisphere.
• The longest day and the shortest night in the Southern Hemisphere.
• The longest night and the shortest day in the Northern Hemisphere.

Question 3.
Which are the days of longest day and longest night in the Northern and Southern Hemispheres?
June 21:

• Longest day in the Northern Hemisphere.
• Longest night in the Southçrn Hemisphere.

December 22:

• Longest day in the Southern Hemisphere.
• Longest night in the Northern Hemisphere.

Question 4.
When is the summer in the Northern Hemisphere? Write the peculiarities of this season.
Summer season is experienced in Northern Hemisphere during June 21 and September 23.
Peculiarities of Summer

• Vertical sun rays and more sunlight.
• Warm atmosphere.

Question 5.
If the earth’s axis was not tilted, where would be the position of sun? What may be its consequences?
The sun would be always near the equator if the earth’s axis was not tilted. Sun rays fall vertically near the equator and the atmosphere gets heated excessively.
Consequences:

• Both the hemispheres receive equal amount of sunlight.
• Equatorial regions experience high temperatures always.
• No change in seasons
• Duration of day and night will be equal.

Question 6.
Which are the two transition seasons between summer and winter? Name the months in which they occur.

• Spring and autumn.
• In Northern Hemisphere, spring season is experienced between 21 March and 21 June. This is the season of transition from winter to summer.
• Autumn is experienced in the Northern Hemisphere from 23 September to 22 December. It marks the transition from summer to winter.

Question 7.
Answer the questions based on the table.

 Latitude Day Night 0° 12 hours 12 hours 17°N 13 hours 11 hours 63 °N 20 hours 4 hours 90°N 6 months Nil

a. Which latitude experiences equal day and night?
b. What is the duration of day at North Pole?
c. Which latitude in the Northern Hemisphere has the longest day?
a. 0° latitude or equator experiences equal day and night.
b. 6 months. This is because the sun is in the Northern Hemisphere.
c. 90°N.

Question 8.
What is meant by local time? Is the local time at each place in India the same? What will be the complications if there are several local times in a country?

• The time estimated at each place based on the apex position of the sun is known as local time.
• The local time is not the same at each place in India.
• If there are several local times in a country, it leads to complications like:

a. Cannot prepare a railway, plane and ship time. table applicable throughout the country.
b. Cannot give information on radio and television programs.
c. Inconvenience in the time schedule of National Day celebrations.

Question 9.
Write the peculiarities of earth’s rotation.

• Day and night are caused due to rotation.
• It takes 24 hours to complete one rotation.
• The earth rotates from west to east and so the sun rises in the eastern side.

Question 10.
The zero degree longitude is called Greenwich line and Prime meridian. Why?

• The zero degree longitude is known as Greenwich line. Time is calculated worldwide based on the Greenwich line. Hence this line is also known as prime meridian.
• Based on the Greenwich line, the world is divided into 24 time zones. The time is ahead to the east of Greenwich line and is behind to the west of Greenwich line. The local time at the Greenwich line is known Greenwich Mean Time.

Question 11.
What is International Date Line? What are its peculiarities?
OR
Write the significance of International Date Line in determining time.
The 180° longitude line from the east and west of Greenwich line is the International Date Line. There is a time difference of 24 hours on both the sides of this line. It creates much difficulty if the same place records two different times with 24 hours difference. To solve this problem, adjustments have been made avoiding the land area along the 180° longitude.

The line is in such a way that it passes through Bering Strait in the Pacific Ocean and avoids some of the inhabited islands. So the International Date Line is not a straight line. The travellers who cross this line from the west calculate time by advancing one day and those who cross the line from the east deduct one day.

Question 12.
What change should be made in time by travellers who cross the International Date Line?

• The travellers who cross this line from the west calculate time by advancing the day and those who cross the line from the east deduct one day.
• The travellers who cross the International Date Line from east to west gain a day and those who cross from west to east, lose a day.

Question 13.
Calculate the time.
The Greenwich time is 4 am on Monday. Calculate the time and date of a place 75°W.
Time is behind the GMT at places lying to the west of Greenwich line. For every 15° longitude, the time decreases by 1 hour. So the time at 75 °W is 5 hours behind GMT.
$$\frac{75}{15}=5$$
The time at Greenwich = Monday 4 am
The time at 75 °W = 5 hours behind GMT
The time and day = Sunday 11 pm;

Question 14.
GMT is 12.00 noon. What is the time at 90°E?
For every 15° longitude, the difference is 1 hour.
In 90° longitude the time difference = $$\frac{90}{15}$$ = 6.
Since it is to east, the time increases.
12.00 + 6 = 6pm.

Question 15.
What are summer solstice and winter solstice? Write their peculiarities.
From 21 March onwards, the sun apparently shifts from the equator northwards and reaches vertically above the Tropic of Cancer on June 21. This day is known as summer solstice in Northern Hemisphere. On this day, the Northern Hemisphere experiences the longest day and shortest night.

From 23 September onwards, the sun apparently shifts from the equator southwards and reaches vertically above the Tropic of Capricorn on December 22. This day is known as winter solstice in Northern Hemisphere. On this day the Northern Hemisphere experiences the shortest day and the longest night.

Question 16.
Examine the changes in the duration of day and night during solstices and equinoxes.
March 21 and September 23 are called equinoxes. The apparent position of the sun on these days will be over equator. Hence the length of day and night will be equal on these days in both the hemispheres.

On June 21, known as summer solstice, the sun will be vertically above the Tropic of Cancer. This is the longest day and the shortest night in the Northern Hemisphere.

On December 22, known as winter solstice, the sun will be vertically above the Tropic of Capricorn. This is the longest night and the shortest day in the Northern Hemisphere.

Question 17.
Write the reasons for the following.
a. Based on a particular longitude, the time is ahead to its east and behind to its west.
b.The length of day increases in Northern Hemisphere after March 21 and upto June 21.
c. There is a time difference of 24 hours on both sides of International Date Line.
a. Time is calculated worldwide based on zero degree longitude or Greenwich meridian. As the earth rotates from west to east, the sun rises first in the eastern side. So the time is ahead to the east and behind to the west of zero degree longitude.

b. The apparent position of sun shifts from the equator to the Northern Hemisphere from March 21 to June 21.

c. There are 180 longitudinal lines to the east and 180 longitudinal lines to the west of zero degree longitude. 180° longitude is known as the International Date Line. Based on Greenwich line, the world is divided into 24 zones, each with a time difference of one hour. So there is a time difference of 24 hours on both the sides of 180° longitude.

Question 18.
Appu celebrated the New Year 2017 exactly at midnight in India. But to his friend Joe in England, it was only sunset.
i. How many hours Joe have to wait for the New Year 2017 to be born?
ii. What is the reason for this time difference?
i. Joe will have to wait for 5 $$\frac{1}{2}$$ hours for the new year. The time of England is 5$$\frac{1}{2}$$ hours behind Indian time. When the new year 2017 was born in India, the time in England was 6.30 pm. on December 31, 2016.

ii. The earth rotates from west to east. So the sun rises first in the eastern side. The time decreases from the east to west by 1 hour for every 15° longitude. The standard meridian of India is 82’/2°E and that of England is 0°. Thus the Indian time is 554 hours ahead of time in England.

Answer the following. Score 4 each.

Question 1.
The Greenwich time is 10 am Monday. Determine the time at 60° E and 60°W
Ans:
60° E 2 pm Monday.$$\frac{60}{15}$$ = 4 hours. 10am +4= 2pm.
60° W 6 am Monday .$$\frac{60}{15}$$ = 4 hours. 10am -4 = 6 am.

Question 2.
One feature each of spring and autumn is given. Add more.

 Spring Autumn Plants sproute Atmospheric temperature decreases considerably

 Spring Autumn Plants sproute Atmospheric temperature decreases considerably. Mango trees bloom Shortening of day and lengthening of night Jack fruit tree bearing buds Trees shed leaves.

Question 3.
Match the items in column A with the items in column B.

 A B Duration of day and night is equal Sun over Tropic of Cancer Trees shed leaves Spring Summer solstice Sun over equator Plants sproute Autumn

 A B Duration of day and night is equal Sun over equator Trees shed leaves Autumn Summer solstice Sun over Tropic of Cancer Plants sproute Spring

Question 4.
Length of day and night will be equal in both the hemispheres on September 23.
i. Why is equal day and night experienced so?
ii. On which other day does the same phenomenon repeat?
iii. How are the above mentioned days known as?
i. The apparent position of the sun on September 23 will be over the equator. Hence the length of day and night will be equal on this day in both the hemispheres.

ii. March 21

iii. Equinoxes

Question 5.
Analyse the following statements and write their reasons.
i. When it is summer in the Northern Hemisphere, it is winter in Southern Hemisphere.
ii. Different seasons occur on the earth.
i. The apparent movement of the sun due to the inclination of axis is the reasons for the occurrence of different seasons. The sun’s rays fall vertically over one hemisphere during one half of the year and on the other hemisphere during the other half. When the sun rays fall vertically in the Northern Hemisphere, it is summer in the Northern Hemisphere and winter in the Southern Hemisphere. Similarly, when the sun rays fall vertically over the Southern Hemisphere, it is summer in the Southern Hemisphere and winter in the Northern Hemisphere.

ii. Reasons for the occurrence of seasons:

• Earth’s revolution
• Inclination of axis
• Migration of the sun

Question 6.
Write the peculiarities of the duration of day and night on 21s’ March, 23rd September, 21s’ June and 22nd December, based on the hints given:

• Apparent position of the sun
• The duration of day and night
• The names by which these days are known.

OR
Write the differences between equinoxes and solstices.
March 21: The apparent position of the sun is over the equator and so equal amount of sunlight is received in both hemispheres. The length of day and night will be equal in both die hemispheres. This day is known as equinox.

June 21: The apparent position of the sun is vertically over the Tropic of Cancer. The day is known as summer solstice in Northern Hemisphere. On this day the Northern Hemisphere experiences its longest day and shortest night.

September 23: The sun comes vertically over the equator. The length of day and night is equal. The day is known as equinox.

December 22: The sun is vertically over the Tropic, of Capricorn. The day is known as winter solstice in Northern Hemisphere. This is the longest night and shortest day in the Northern Hemisphere.

Question 7.
Explain the terms ‘Utharayanam ’ and ‘Dakshinayanam ’. What changes occur in, the duration of day in Northern Hemisphere during these periods?
The northward apparent movement of the sun from Tropic of Capricorn to Tropic of Cancer is termed as Utharayanam. The duration of day in the Northern Hemisphere gradually increases during this period. The duration of day in the Southern Hemisphere gradually decreases.

The southward apparent movement of the sun from Tropic of Cancer to Tropic of Capricorn is termed as Dakshinayanam. The duration of day in the Northern Hemisphere gradually decreases and that of Southern Hemisphere gradually increases.

Answer the following. Score 5/6 each.

Question 1.
Spring and autumn are transition seasons between summer and winter. Explain.
Spring and autumn are two transition seasons.

1. Spring: Spring is the season of transition from winter to summer. The peculiarities of spring are plants sprouting, mango trees blooming and jack fruit tree bearing buds. It is experienced between 21 March and 21 June in the Northern Hemisphere.
2. Autumn : Autumn marks the transition from the severity of summer towards winter. During this period, the atmospheric temperature decreases considerably. This is followed by a shortening of day and lengthening of night. The trees generally shed their leaves. Autumn is experienced in the Northern Hemisphere from 23 September to 22 December.

Question 2.
What are the reasons for the occurrence of seasons?
Variations in the amount of sunshine received are the basis for the occurrence of different seasons. The reasons for the occurrence of different seasons are,

• Revolution of the earth
• Tilt of the earth’ axis
• Apparent movement of the sun
• Revolution of the earth: The earth revolves around the sun in an elliptical orbit. This motion is known as revolution. The earth takes 365$$\frac{1}{4}$$ days to complete one revolution.
• Tilt of the earth’s axis: The axis of the earth is tilted at an angle of 66$$\frac{1}{2}$$° from the orbital plane and 23$$\frac{1}{2}$$° from the vertical plane.

The earth maintains this tilt throughout its revolution. This is known as parallelism ofthe earth’s axis. Since the parallelism is maintained throughout the revolution, the position of the sun in relation to the earth varies.

Apparent movement of the sun : The sun shifts apparently between Tropic of Cancer and Tropic of Capricorn. This is known as the apparent movement of the sun. There will be variation in the amount of solar energy received on earth due to the apparent movement of the sun.

The sun rays fall vertically over one hemisphere during one half of the year and on the other hemisphere during the other half. Temperature will be higher over places where the vertical rays ofthe sun fall. The temperature will be low at places where the sun rays are slanting.

Question 3.
Complete the table related to change in season.

Question 4.
The shift in the relative position of the sun causes the occurrence of seasons. Based on this statement, prepare a table on the different seasons experienced in the Northern and Southern Hemispheres.

Question 5.
Answer the following questions based on global determination of time?
i. By what name is the time estimated based on the apex position of the sun known?
ii. What are the practical difficulties in determining time based on the apex position of sun?
iii. How is time determined by countries as a solution to this?
iv. How is Indian Standard Time estimated?
i. The time estimated at each place, based on the apex position of the sun is termed as local time.

ii. Cannot prepare a railway/flight/examination time table throughout the country. Cannot give information on radio/television program.

iii. To solve this, the local time at the longitude that passes through the middle of a country is selected as the common time for the whole country. Each country considers the longitude that passes almost through its middle as the standard meridian. The local time at the standard meridian is the standard time of the country.

iv. Each country in the world considers the longitude that passes almost through its middle as the standard meridian. The longitudinal extent of India is from 68°E to 97°E. This amounts roughly to 300. The 82$$\frac{1}{2}$$ E longitude passes almost through the middle of these longitudes. So 82$$\frac{1}{2}$$°E longitude is considered as the standard meridian of India.

Question 6.
The picture depicts the seasons experienced in the Northern Hemisphere.
i. Which seasons are represented by the letters A and B?
ii. Write the peculiarities of the transition seasons.
iii. What are the reasons for the occurrence of seasons?

i.
A. Spring
B. Autumn

ii. Spring.

• Season of transition from winter to summer.
• Plants sprout, mango trees bloom.

Autumn

• Transition from severity of summer towards winter.
• Atmospheric temperature decreases considerably during this period.
• Shortening of day and lengthening of night.
• Trees shed leaves.

iii. The apparent movement of the sun due to the inclination of the axis. Revolution.

Question 7.
What is the difference between local time and standard time? Why do countries follow a standard time? Calculate Indian Standard time when Greenwich time is 6.30 in the morning.
Local time: The time estimated at each place based on the apex position of the sun is termed as the local time.

Standard time: Each country in the world considers the longitude that passes almost through its middle as the standard meridian. The local time at the standard meridian is the standard time.

Why standard time? : The local time would be different at each longitude. If we start calculating local time at different places based on the longitude there, it would create lot of confusion. To solve this, the local time at the longitude that passes through the middle of a country is selected as the common time for the whole country.

The longitude of Greenwich is 0°
The Standard Meridian of India is 82$$\frac{1}{2}$$°E Indian Standard Time is 5$$\frac{1}{2}$$ hours ahead of Greenwich time.
When the time is 6.30 am in Greenwich, the time in India is 6.30 + 5.30 = 12 = 12 noon

Question 8.
Write on the seasons experienced in Northern Hemisphere due to the apparent movement of the sun between the Tropic of Cancer and the Tropic of Capricorn.
As a result of the apparent movement of the sun between Tropic of Cancer and Tropic of Capricorn, the different seasons like spring, summer, autumn and winter get repeated in a cyclic manner.
The apparent position of the sun will be over the equator on March 21 and September 23. So equal amount of sunlight is received in both the hemispheres.

Hence the length of day and night will be equal on these days in. both the hemispheres. These days are called equinoxes. From March 21 onwards, the sun apparently shifts from the equator northwards and reaches vertically over the Tropic of Cancer on June 21.

This day is known as the summer solstice in Northern Hemisphere. From September 23 onwards, the sun apparently shifts from the equator southwards and reaches vertically over the Tropic of Capricorn on December 22. This day is known as winter solstice in Northern Hemisphere.

The Northern Hemisphere generally experiences spring season between 21 March and 21 June. Spring is the season of transition from winter to summer.

The southward apparent movement of the sun begins from June 21 and again reaches vertically above the equator on 23 September. Summer season is experienced in the Northern Hemisphere during this period.

Autumn season is experienced in the Northern Hemisphere from 23 September to 22 December. Autumn marks the transition from the severity of summer towards winter.

The northward apparent shift of the sun begins by 22 December and again reaches vertically above the equator on 21 March. This period marks the winter season in Northern Hemisphere.

Question 9.
When the local time of Alexandria (30°E) in Egypt is 6 am on Monday morning, what will be the local time of New Orleans (90°W) in USA?

• The longitudinal extent from Greenwich to Alexandria: 30°.
• The longitudinal extent from Greenwich to New Orleans: 90°.
• The total longitudinal extent from A lexandria to Greenwich: 120°.
• The difference of 1 ° longitude: 4 minutes.
• The difference of 15° longitude : 15 x 4 = 60 minutes or 1 hour.
• The difference of 120° longitude in minutes: 120 x 4 = 480 minutes.
In hours :$$\frac{120}{15}$$ = 8 hours.
• Time is 1 hour ahead for each 15° longitude from west to east. Similarly time is 1 hour behind for each 15° longitude from east to west.
• New Orleans is located to the west of Alexandria and the time there will be 8 hours behind the time of Alexandria.
• The time at New Orleans will be 10 pm on Sunday.

Question 10.
When it is Saturday 8 p.m at 90°W, what will be the time of 120°E?

• Longitudinal extent from Greenwich to 90°W:90°.
• Longitudinal extent from Greenwich to 120°F: 120°.
Total longitudinal extent : 2100(90+ 120).
• The difference of 15° longitude: 1 hour.
• The difference of 210° longitude : $$\frac{120}{15}$$ = 14 hours. .
• For each 150 longitudes, time will be ahead by 1 hour from west to east.
• The time at 120°E will be ahead by 14 hours from the time at 90°W.
• The time of 120°E will be Sunday 10 a.m.

Question 11.
It is Monday 4.30 pm in India. Calculate the time at 78°W.

• Longitudinal extent from Greenwich to 78° W: 78°.
• Longitudinal extent from Greenwich to India (82$$\frac{1}{2}$$ °E): 82$$\frac{1}{2}$$ °.
• Total longitudinal extent: 16$$\frac{1}{2}$$°. (78 + 82$$\frac{1}{2}$$°)
• The difference for 10 longitude: 4 minutes.
• The difference for $$\frac{1}{2}$$°0 longitude : 2 minutes
• The difference for 16$$\frac{1}{2}$$0
in minutes = 160° x 4 = 642 minutes
in hours = $$\frac{642}{60}$$= 10 hours 42 minutes.
• From east to west, time will be behind 1 hour for each 15° longitude.
• The time at 78°W will be 10 hours 42 minutes behind the time of India.
• It is 5.48 am on Monday.

Question 12.
When the Greenwich time was 2 pm on Wednesday, it was 10 pm in Australia and 11 am in Brazil. Calculate the longitude of Australia and Brazil.

Brazil

• Time difference between Greenwich and Brazil: 3 hours behind.
• If the time is behind Greenwich time, the place will be in western longitude.
• The time required to complete 360° rotation is 24 hours. The longitudinal extent covered by earth in 1 hour=$$\frac{360}{24}$$ = 15°.
• The longitudinal extent of Brazil from Greenwich: 3 x 15° = 45°W.
• The longitude of Brazil: 45°W.

Australia

• Time difference between Greenwich and Australia 8 hours ahead.
• As the time is ahead, the place will be in eastern longitude.
• The longitudinal extent covered by earth in I hour: 15°.
• The longitudinal extent of Australia from Greenwich: 8 x 15° = 120°.
• The longitude of Australia: 120°E.

Kerala Syllabus 10th Standard Social Science Important Questions