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Solutions for Geography, Class 9, ICSE
See the below figure and answer the following questions.
(a) What would be the value of angle AOB?
(b) The circle through EQ is a
(c) Identify the relationship between length of the Prime Meridian and that of 40° Meridian.
(a) 40°
(b) Great circle
(c) =
Assertion (A): 1° angular distance of the parallels of latitudes is roughly equal to 111 km.
Reason (R) : The poles are each located at 90° angular distance north or south of the Equator.
Both A and R are true but R does not explain A.
Explanation — The length of the Equator is equal to the circumference of the earth or 40,075 km. Since the circumference of a circle is equal to 360°, the 1° angular distance is roughly equal to 111 km.
Assertion (A): All places on a particular meridian will have noon at the same time.
Reason (R): The sun crosses a meridian at noon.
Both A and R are true and R is the correct explanation of A.
Explanation — Noon occurs when the sun is exactly overhead on a meridian, so all places along the same meridian experience noon at the same time. The sun appears to move from east to west across the sky and crosses the meridian at its highest point, which is why this moment is called noon.
Assertion (A): For each 1° longitude towards the East, 4 minutes are to be added and each 1° longitude towards the West, 4 minutes are to be subtracted.
Reason (R): The earth rotates on its axis from East to West.
A is true but R is false.
Explanation — The Earth makes a complete circle on its axis — it covers 360° longitudes in 24 hours. That is to say, it covers every 15° longitudes in one hour or 1° longitude every 4 minutes. The earth rotates on its axis from West to East.
Crossed the IDL
Explanation — When you cross the International Date Line (IDL) from west to east, you lose a day because the calendar moves back by one day. The IDL is an imaginary line where the date changes by one day when crossed.
12:00 noon
Explanation — Fiji is about 12 hours ahead of Greenwich Mean Time (GMT). So, when it is midnight (12:00 am) in Fiji, it would be 12 hours earlier — that is 12:00 noon of the previous day in London (GMT).
equal to the radius of the sphere
Assertion (A): There is a time difference of a full day on crossing the IDL.
Reason (R): It is diametrically opposite the Greenwich Meridian.
Both A and R are true and R is the correct explanation of A.
Explanation — The line of longitude 180° or IDL is one and the same for East or West of the Prime Meridian. Since it is diametrically opposite to the Greenwich Meridian it causes a time difference of a full day on crossing the line. The time difference works out to 12 hours (180° x 4 min) from either side. Thus, on crossing the line, a day is gained or lost.
Assertion (A): Great circles are used to find the shortest distance between any two points on the earth's surface.
Reason (R): Great circle routes take into account weather or political restrictions.
A is true but R is false.
Explanation — A Great Circle Route is the shortest distance between two places on the earth and lies on the arc of a great circle. Using this hypothesis, navigators find the shortest distance between any two points on the earth's surface.
A framework of lines of longitude and latitude on a globe or a map is called a geographic grid.
This grid on the globe or the map serves the same purpose as the system of coordinates on the x-axis and y-axis on a graph paper. In this case the x-axis is represented by lines of latitude (horizontal) and y-axis, by lines of longitude (vertical). These lines help to locate places on the earth.
The imaginary lines running east to west, parallel to the equator are called lines of latitude.
The imaginary lines running north to south passing through the poles are called lines of longitude.
Eratosthenes, the Greek philosopher, devised the lines of latitude and longitude.
Two characteristics of lines of latitude are:
The two hemispheres of the earth made by the Equator are-
The thermal zones of the earth are-
Two uses of the lines of latitude are:
The angular distance of 1° latitude is equal to 111 km.
The Prime Meridian is the line of longitude whose angular distance is defined as 0 degrees. It passes through Greenwich near London.
While fixing the Time Zones, the time at Prime Meridian has been selected as the mean time. The time for all the other places is calculated with reference to the time at Prime Meridian.
Lines of latitude divide the earth into three distinct heat belts -
The lines of latitude indicate the general climate of the area by applying the principle of heat zones of the earth.
Prime Meridian is used to fix the World Standard Time.
Its value in degrees is 0°.
The longitudinal value of Indian Standard Meridian is 82° 30'E.
Two characteristics of the Great Circles are:
Two uses of the Great Circles are:
A great circle route is the shortest distance between two places on the earth and lies on the arc of a great circle.
Great Circle Routes are specially important for places that are on opposite sides of the globe.
These lines of latitude form one of the coordinates of the grid system. The lines of latitude have the following significance-
(i) Lines of latitude are called parallels of latitude as these lines are parallel to the Equator and each other.
(ii) Lines of latitude are not of equal length as they become smaller as we move towards the poles.
(iii) Lines of latitude carve out the heat zones of the earth as the temperature goes on decreasing from the equator towards the poles. Thus, these lines indicate the general climate of an area by applying the principle of heat zones.
The earth makes a complete circle on its axis covering 360° in 24 hours. It covers 1° longitude every 4 minutes. For each 1° longitude towards the east, 4 minutes are to be added and for each 1° longitude towards the west, 4 minutes are to be subtracted.
(i) Lines of longitude are called meridians of longitude because the sun crosses a meridian at noon. So, all places on a particular meridian will have noon at the same time.
(ii) Lines of longitude are of same length as they all converge at the poles.
(iii) Diametrically opposite lines of longitude and the Equator are called Great Circles because they pass through or touch the centre of the circle. Also, they have a radius equal to the radius of the sphere's centre.
The line of longitude 180° is one and the same for east or west of the Prime Meridian. Since it is diametrically opposite to the Greenwich Meridian, it causes a time difference of a full day on crossing the line.
The International Date Line is the 180° line. When crossing this date line from the west to east a day is deducted or the time is fixed backward by one day. When crossing the International Date Line, from east to west, a day is added.
The International Date Line is the 180° line. When crossing this date line from the west to east a day is deducted or the time is fixed backward by one day. When crossing the International Date Line, from east to west, a day is added.
For example, if it is 8 pm Monday 25th December at Greenwich, it will be 8 am Tuesday, 26th December on crossing the 180° line from the east as time will be 12 hours ahead. But if one were to travel from west, it will be 12 hours behind or 8 am Monday, 25th December.
Give a geographical reason for each of the following:
(i) The International Date Line deviates and goes zig-zag near some islands in the Pacific Ocean.
(ii) The Greenwich time is called the Greenwich Mean Time.
(iii) Great Circles are the shortest routes between two places.
(i) The International Date Line deviates and goes zig-zag near some islands in the Pacific Ocean to avoid the confusion of having different dates within the same country.
(ii) The Greenwich time is called the Greenwich Mean Time as while fixing the time zones, the time at Greenwich has been selected as the mean time and provides the basis for calculating the Standard Time of other places.
(iii) Great Circles are the shortest routes between two places as we can connect any two places on the earth's surface by the curvature line of the great circle. And this curvature is the smallest possible route between those two places, because this curvature directly connects those places or points.
As the earth takes 24 hours to make a complete rotation along its axis crossing 360° lines of longitude, so earth takes nearly 4 minutes to move 1° longitude.
For example, Indian Standard Time is based on 82 1/2° E longitude. So if the time in India is 12 noon, so it will be 6.30 A.M. in England or GMT.
The time difference between 0° and 82 1/2° E will be-
82.5 × 4 = 330 minutes or 330 ÷ 60 = 5 1/2 hours
So there is difference of 5 1/2 hours between India and England, as England lies in the west, so the time will be 5 1/2 hours less than India.
The latitude of my city is 26° 55' N.
My city lies in the North Temperate zone which is between 23½°N to 66½°N. This region experiences moderate climate i.e., the temperature is neither too hot nor too cold.
My home town is located near the poles as it receives slanting rays of the sun. Slanting rays lose more heat while travelling and result in cooler temperature. On the other hand, my boarding school is located near the equator as it receives vertical rays of the sun resulting in higher temperature.
Russia has the maximum number of time zones in the world, with a total of 11 time zones. The reason behind a country having multiple time zones is due to its geographical size and location. As the earth rotates, each 15° change in longitude corresponds to a one-hour difference in time. Therefore, a country that spans several longitudes, like Russia or the United States, may have multiple time zones to account for the variations in local time.
In the case of India, the country is geographically smaller and spans fewer longitudes compared to a country like Russia. Therefore, India has one time zone to maintain uniformity across the country.
Some countries like Australia, New Zealand, and Japan welcome the New Year before India because of the differences in time zones. These countries are located ahead of India in terms of longitude, and therefore, they are several hours ahead in time.
Australia and New Zealand are located in the eastern hemisphere and are ahead of India in terms of time zones. Japan is located in the same time zone as Australia and also welcomes the New Year before India.
